Yes! There is. It's called WINE, go to www.winehq.org to check it out. Be warned that compatibility is still an issue but I've personally had quite a few successes.

Wine is definitly the way to go. A place to look to improve your experience with wine is Franks Corner, which has some tips for getting certain programs to run, and some useful links.

Also, let us know what programs that you are looking to run. We may save you some time. Frank's Corner is a good site, but it is getting outdated in information related to productivity apps.

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!

OldSpiceAP makes a great point. I don't use wine at all I always find the open source equivilant.

But there aren't always open-source equivalents for every piece of software. That's where wine comes in.

I've been lucky I guess because the only time I need my windows box is for gaming. Wine is not there yet and for gameing imo. For everything else I use my linux box and oss. I don't miss any of those windows apps at all.

That's what many people say. Wine is fine, except that it supports only a very limited number of windows apps. Even Codeweavers states that it only supports 10 or 11 apps fully. The problem is, that most folks are looking for being able to use fairly complex programs with wine, such as Photoshop and the like.
 
Gaming is coming along and is a work in progress. DapperDan has some tips on Cedega, which is a flavor of wine for gaming. This package seems more promising for gamers. Frank's Corner is a good place to start in able to get a good idea what the status is of various flavors of wine.

I never could have imagined that Winex/Cedega would improve as much as it has over the last year and a half. With the old Winex, Trespasser wouldn't even run, and none of the option would work. That has improved to such a degree that Trespasser, under the current version, runs as well as in Windows in software mode. In fact, it may even run better!

Not always an open source equivalent? OK maybe - but I think you'd be hard pressed to find a program that doesn't have an open source equivalent, except for games. Check out this link:
 
http://linuxshop.mu/linuxbegin/win-lin-soft-en/table.shtml
 
I'd give that a shot just for starters if you are having trouble with finding a linux equivalent for a program.

That's quite an impressive list OldSpiceAP! That's a really good find! I knew Linux was more versatile when it came to varieties of software, but I had no idea how much so! Thanks for than link!

Wine is really quite impressive now. I've managed to get star wars jedi academy and call of duty running perfectly using it.