By using bookmarklets, you can compensate for Chrome’s lack of support for extensions. You can create a customized toolbar to utilize the functionality of other sites like StumbleUpon, Delicious, Evernote, and others.
Here’s some good bookmarklets to start with. Simply drag any of these links to Chrome’s Bookmarks bar:
Submit to StumbleUpon
Take Screenshot
Supercharged GmailThis (via Lifehacker)
What bookmarklets do you use?