Selenium2, by default, starts firefox with a fresh profile. I like that for a default, but for some good reasons (access to my bookmarks, saved passwords, use my add-ons, et
Simon Stewart answered this on the mailing list for me.
To summarize his reply: you take your firefox profile, zip it up (zip, not tgz), base64-encode it, then send the whole thing as a /session json request (put the base64 string in the firefox_profile key of the Capabilities object).
An example way to do this on Linux:
cd /your/profile
zip -r profile *
base64 profile.zip > profile.zip.b64
And then if you're using PHPWebDriver when connecting do:
$webdriver->connect("firefox", "", array("firefox_profile" => file_get_contents("/your/profile/profile.zip.b64")))
NOTE: It still won't be my real profile, rather a copy of it. So bookmarks won't be remembered, the cache won't be filled, etc.