http://www.cakewalk.com
large selection of stuff there
My wife uses mac and has garage band which I messed around with. seems to be geared towards looping/tracking/recording. The equiv product from cakewalk for windows would be SONAR Home Studio 4 XL which I have been using for about a month - omg.
If asked to compare, I'd say HS blows GB out of the water, but thats just mho. I think the cw site wanted $229.00 for hs4xl but I went online and got it from guitar center for $159.00. If youre doing looping youll want xl since it includes a load of samples. If you're doing tracking (audio/midi) then you can save a few dollars and skip the xl bit and just get sonar hs 4.
I am doing strictly Audio tracking (and maybe midi too) but I am not intersted in loops etc so just going on that I found HS4XL perfect for me. Cake has a ton of packages geared towards certain tasks so you may not even want anything in the HS family - read up on their site.
But as with anything,
research everything before you buy anything