For its integrity, features and functionality, GMail is the leading webmail application worldwide. For the same reasons, Firefox tends to be the most used browser out there.
As you well know, Firefox can be customized to its full, with the help of plugins and scripts. For example, GreaseMonkey is a Mozilla Firefox extension that allows users to install scripts that make on-the-fly changes to specific web pages. As the Greasemonkey scripts are persistent, the changes made to the web pages are executed every time the page is opened, making them effectively permanent for the user running the script.
Greasemonkey can be used for adding new functionality to web pages, fixing rendering bugs, combining data from multiple webpages, and numerous other purposes. Well written Greasemonkey scripts can integrate changes so well that their additions appear to be natural parts of the web page. I'm going to present the most useful 10 plugins and tweaks to be used with GMail.
Make sure you run decent versions of Firefox and GreaseMonkey before you try to install or run anything shown here. I've also included some screenshots of the effects those scripts have on your GMail, so make sure you check them out by clicking the thumbnail to see the large picture.
1. A super clean/white GMail interface
Install instructions | Known issues | Understanding the script
Gmail Super Clean was made to simplify the way Gmail looks. It's got quite a few customization options. You can change the logo, fonts, show/hide ads and many more, using the User script commands on Greasemonkey. The script is also made public on userscripts.org and statistics show that almost 50,000 people installed it.
2. GMail logo changer
Install / View source
By default, the upper left GMail logo is this. If you got tired of it, this script is exactly what you're looking for. It will allow you to change the logo to an image of your own, exactly as it happens on the e-mail service from Google Apps.
3. Folders in GMail
Installation Instructions
This is perfect for you if you liked the folder-like sorting options in the other e-mail solutions, but you rather stick to GMail. Now you can have them both by installing this plugin. Have a look at the before-after timeline and if you think it'd work for you, go ahead and try out the script. If you're not convinced yet, here's how it works:
If you have two labels, Mum and Dad and you want them to be subfolders of Family, you need to create three labels: Family, Family\Mum and Family\Dad . In the left you can see how the labels will look before the script, and on the right you can see how the script interprets them. Neat, huh? This script is available for IE7 and Opera9, with the help of additional plugins similar to GreaseMonkey.
4. One click conversations
Plugin page | Install the script
One Click Conversations is a java script for enhancing GMail.
GMail view must be set to "standard with chat" in order for this script to work. It adds an icon just to the left of sender name in list view and in message view so you can access it easily. Clicking on icon takes you to the recent conversations with that user. Rolling over icon in message view pops up menu, as found via the "quick contacts" panel.
As you can see, it adds one click access to recent conversations with each of your contacts. The demo below should explain things succinctly. Have a look and see exactly what I'm talking about.
5. HTML signatures (multiple signatures if you want)
View script source / Install script
HTML in GMail signatures has been an issue since the service was started. Some of us use multiple e-mail addresses, therefore we need multiple signatures, and some of them need to be HTML compatible. I noticed this plugin also fixes the signature placement bug. By default, your signature was placed at the end of the message, no matter if you were composing a new one or replying to an existent one. In the second situation, your reply would have been on top and the signature was placed to the bottom, thus being separated.
The plugin actually creates a link that you can click to insert an HTML signature into a GMail message. Like I said, it supports multiple signatures. Just add a variable at the top that has your HTML in it. Then add that variable name to the array "sigs". If you have one signature, just make sure that one variable name is in the array. If you have more than one, it will prompt you (on insertion) for which one. Otherwise it just inserts it.
6. GMail + Google Calendar
View source / Install script
This embeds Google Calendar to Gmail by adding a "Calendar" link. The position of the calendar link can be changed by editing the source and modifying the CALENDAR_LINK_POSITION constant (if you don't see the constant, please update the script). Currently it can only be moved from before the Inbox link to after the Trash link. I'll try to add more flexibility later.
If you want the Calendar menus aligned at the right of the screen, update the script and edit the source. Check the CALENDAR_STYLES part, you'll see some commented code, just uncomment it. However this isn't very useful because the popups for Quick Add and the Calendars settings will appear out of the screen, I hope to fix this in the near future.
7. GMail conversation preview
View source / Install script
The script allows you to get a preview bubble when you right click ANY conversation in GMail. It addresses the broken Archive and Trash features. Also contains some personalizations including a Subject bar below the link toolbar.
8. Google Reader integration
View source / Install script
This doesn't need a description. It's just a nice integration of Google Reader, along with other author implementations I'm going to mention below.
*Moved Collapse Gmail link to under Compose Mail
* Removed unnessasary spaces
* Added Google Reader favicon to Reader link
* Added a Launch Reader link to open Google Reader in a new window
* Added a Home link
* Made Reader's labels collapsable
9. GMail label colors
View source / Install script | Official webpage
Ignoring the folders vs. labels debate for now I always wondered why labels in Gmail cannot be color-coded. This script adds that functionality, since it turns out to be very useful (if used sparingly, otherwise too many colors can get overwhelming). To specify a color, simply rename a label to "Labelname #color" ( e.g. to make the label "Foo" be red, use "Foo #red" and to make the label "Bar" be orange, use "Bar ##d52″). It works in a similar way to the conversation bubble script, in that it overrides the JavaScript function through which Gmail receives data. It has to jump through some hoops to avoid the HTML escaping that Gmail does; intrepid Greasemonkey hackers may want to look at the source.
10. GMail macros
View source / Install script | Official webpage
Gmail Macros adds additional keyboard shortcuts to Gmail. Some are obvious (and have been done by other scripts) such as "t" for move to trash and "r" for mark as read. However, the author strove to provide a bit more functionality. For example, "p" both marks a message as read and archives it, when you really don't want to read something (the "p" stands for "purge"). Additionally, the shortcuts can be easily customized by editing the HANDLERS_TABLE constant. More than one action can be chained together by providing a list of action codes (which are contained in the script and were extracted by looking at the generated "More Actions..." menu in Gmail). The other novel feature is for label operations. Pressing "g" brings up a Quicksilver-like display that allows you to begin typing in a label name to go to it (special names like "Inbox" and "Trash" work too). Similarly, pressing "l" allows you to label a conversation with the label of your choosing.
That was it. The world of GreaseMonkey scripts is fairly large, but that's a good thing. There's plenty of GMail plugins to choose from, in order to make your life easier and enhance your GMail experience.