In Firefox 2.0- (versions prior to 2.0) I used the Session Saver extention to keep my pages across browsing sessions.  Essentially, I could close my browser and then re-open it and the websites that I was browsing before would come up, even if the browser crashed or the computer unexpectedly shut off.

In 2.0+ the Session Saver extention doesn't have an updated version.  After a little digging I think I know why, because it's now built in, but it's a bit hidden for some wierd reason (or at least I didn't see a check box).  To get it working follow the steps below:

In the address bar type in "about:config".  In the "Filter" box put "browser.startup.page".  Double click the value that shows up below and then enter the value "3" where it now has a "1".   That was about as intuitive as installing SuSE Linux, except way easier!