Shoutbox

Hey guys, i'm considering using linux on one of my computers, and im just wondering a few things... what distributions  do people think are the best? and what programs would you guys recommend i use? internet browsersm office alternative, antivirus/spyware/adware etc, firewalls etc etc. i really have no idea with linux, but i'm always wanting to find out some new things and im really looking for a change! also how easy is it to take linux off a computer and put windows back on it? probably just a matter of formatting the hard drive?

thanks for your help (in advance)