What's the best way to manage multiple Google Accounts?

I highly recommend using the Chrome browser, and then setting up separate Chrome profiles (http://www.labnol.org/software/c...).  You'll then essentially be able to run separate instances of Chrome, each with its own cookies, bookmarks, and, yes, signins (for Google and other services).

Additional tip:  Set different Themes (Options -> Personal Stuff -> Themes) for each profile, so you can quickly tell at a glance which browser window is logged into which account.  This will save you from accidentally sending that lovey dovey e-mail from your work account ;).