Wine is definately a good place to start, but there are comercial verisions of wine that could be useful as well. Codeweavers CrossoverOffice is a good program for applications such as Photoshop, Tables, Microshaft Office, Paintshop Pro, Winamp, Quicktime and Windows Media Player, as well as Internet Explorer. I wouldn't bother with any of these programs though as their Linux equivalants are either just as good or better.
Gimp - replaces photoshop or paintshop. Intuative interface - great program.
OpenOffice - a full office suit. I like its features better than MS office.
Internet Explorer - Mozilla Firefox, Mozilla, Galeon, Konqueror, Opera, Lynks - they are all good but I prefer Firefox.
Quicktime and Windows Media Player - Mplayer will play just about any media file ever.
Winamp - XMMS - can ecen use winamp skins with a little tweaking.
I've had good success with wine and CXOffice but I've found that the native programs are just as good and free - think of how much it costs to but a new version of MS office every couple years - Open Office is free - as are new versions of it. Plus it will read MS office files - even powerpoint presentations.
If you are intersted in games and wine doesn't run them try transgamings Cedega - its another comercial version of wine that runs many windows only games. its only a few bucks and its worth it - I have had good successwith it as well.
Here is what I use wine for:
CXOffice - Starcraft - works perfectly
Cedega - Diablo II - perfect.
Wine - Age of Empires II - The Conquerors Expansion.
Wine - neverwinter nights (but now I use the native version)
I also occasionally use wine for Diablo II - both work fine.
Good luck!