If you don't mind tweaking the settings for proper performance, I highly recommend HTTPSwitchboard.
I also use a version of AdBlock, ScriptBlock, FlashBlock (not sure if I need that but I used it a lot in the past with other browsers), and Ghostery. HTTPSB can replace ScriptBlock when configured right but ScriptBlock is so easy I have it there anyway.
Another one I think is neat is Extension Automation, which lets you enable/disable extensions for specific sites. And I have a couple of the ones that give IP address info, specifically IP Domain Country Flag (because I got used to Flagfox) and IP Address and Domain Information for more detail. The latter one does not take up any memory (per Task Mgr) until you open it, which is kind of rare for extensions (I've seen that only with a few others).
I have also installed HTTPS Everywhere even though I am not all that sure that trying to use https all the time is a good idea. I know about keeping the data exchanged encrypted, just not sure about other issues, but I wanted to try it to see how well it would work. So, can't recommend this one necessarily, yet.