I’m posting code snippets in reply to questions on one of the jQuery mailing lists a few times daily. Rather annoying is the lack of support for indentation: I have to use spaces one-by-one to indent code.
Usage: Drag above link to your bookmarks. Open GMail and click on the reply-textarea within a thread. Activate the bookmarklet and give the textarea focus again. Use the Tab key to input tabs!
There are more ideas at hand: Unindent code pasted from source files, unindent a line with shift-tab, (un)indent multiple lines (via usual text selection).
Feel free to contribute, ideas and code welcome!
Update: Now it also sets the font-family to “Courier New”, giving you a monospace font for easier visual indentation.