Remember Gmail Redesigned, the Firefox extension that turns Gmail from ugly HTML-ish duckling to beautiful Web 2.0-style swan? If you didn't try it then, you might be even more tempted now: Gmail Redesigned 3.0 offers both layout and performance improvements while maintaining that gorgeous Gmail front end. Here's a peek:
The extension is also half the size of its predecessor, meaning it loads more quickly. (My informal test bear this out: Gmail fired right up, whereas with GR 2.0 there was a noticeable delay.)
In addition, Gmail Redesigned now includes support for Google Contacts and Google Chat windows. In short, it makes your entire Web-based Gmail experience much easier on the eyes.
If you're already using Google Redesigned (which gussies up Google Calendar and Google Reader as well), then the Gmail Redesigned 3.0 update should already be on your system. If not, you can get it here.
Of course, if you'd rather not bother with extensions and all that, you can spruce up Gmail with Google's own themes. But that's just face paint; Gmail Redesigned gives it more of an extreme makeover (without all the schmaltz and bawling at the end).