google is your friend, friend. just search for what you're looking for
fireworks tutorial rollover
photoshop slice template
gimp is about as good a free program as you'll find although if you're used to anything else, it will take time to adjust. you might run across free trials for the commercial stuff like photoshop, illustrator, fireworks and paint shop pro. of those, paint shop pro is the least expensive.
the best sources for free software are
http://www.sourceforge.net (open source) and
http://www.nonags.com/nonags (windows freeware)
i use fireworks and paint shop pro. i cannot vouch for paint shop pro's most recent versions as mine is a pre-corel one. and i have no idea what'll happen to fireworks now that adobe owns macromedia and has it's own programs that overlap. i have illustrator and photoshop but find myself returning to one of the others all the time instead.
golive has the best in-program css editor, i think, but it's a pretty sucky program for layout work. i usually just do edits to css while having a static page loaded up in the browser in one window and the css in a text editor. edit -- save -- refresh browser -- repeat. nano or gedit on linux or notepad++ on windows (all three with syntax highlighting) for the editor. and if i'm not editing html in one of those editors, then it's in dreamweaver and i might hack at the styles using it, but i still prefer a regular text editor for css.
if you want a program specifically for editing css, take a peek at topstyle lite. it is bundled with a few html editors and is also available separately (for free) see
http://www.bradsoft.com/download/index.asp there's also a commercial 'pro' version with more features.