Open Source Replacements for Proprietary Software Applications
What's the app people use most? I'd say it's a browser. I've already talked a bit about open source browsers HERE, but suffice to say that Internet Explorer is NOT where it's at. IE6 was a disaster in the world of html as far as I'm concerned (and a lot of other web designers will agree) Web designers who wanted to be standards compliant had to make the real site, and then go break it so that it would render properly in IE6. Newer versions of IE are probably more standards compliant, but I think you're better off just using something else. Firefox, K-Meleon (built on the same engine, but lighter weight), and Chromium are just some of the open source browsers you'd be more than happy with that render pages properly and run quickly. There are even some text only browsers, if you're really looking for speed. I've been known to use elinks every now and again, like when I'm on a less than speedy internet connection.
There are a few different office apps you can use to replace Microsoft's package. For total replacement of every application, you'd probably want to go grab either OpenOffice or LibreOffice. At this point, they're very similar, maybe even the same app. Both read and write to Microsoft file formats and open document formats.
Since LibreOffice forked off of the OpenOffice development tree, I suspect they'll get more different as time goes by. I've thrown my eggs in the LibreOffice basket, only because I think a regular community will run things better than Oracle. Oracle, if you didn't know, is a gigantic software company who bought Sun Microsystems, and hence stands kind of at the helm of the OpenOffice boat.
For just a word processer, you might do fine with something like AbiWord. It does a fine job, reads and writes to the open text document and Microsoft's Word format.
When you want a stand alone spreadsheet application, Gnumeric might be up your alley. Like Abiword, it opens the open document (spreadsheet in this case) and Microsoft Office formats.
Notepad is the default plain text editor. Oddly enough, it doesn't edit plain text files very well. Instead it insert all sorts of wonky characters into text documents. I've found that Geany, Gedit, Notepad++ (only for Windows), and a couple of others are wonderful open source replacements for the default Windows text editor. Most have some sort of syntax highlighting, something that helps a lot when your writing something like html code, php, or java.
While this might be like using a wrecking ball to tap a finish nail, GIMP is the image editor I've used for years. If all you want to do is crop or resize a bunch of images, this might be too much software for you. But if you want an open source replacement for Adobe Photoshop with nearly all the functionality, then GIMP is for you. I'm not sure what you can do in Photoshop that you can't do in GIMP, since I never came near to being a power user of Photoshop back before I found GIMP. The only thing I missed after switching was the ability to group layers. This might be possible with some sort of add on nowadays.
While this shouldn't really apply to small businesses, it might…
Do you have any idea how many open source games are our there? Just looking in the Ubuntu repositories reveals a daunting number of them, and that's not everything out there by a long shot. Go on SourceForge.net and search for games. You'll find a pile of them.
And just like regular proprietary games, many of them are rather “bleah,” but lots are very good. Some of my favorites are Liquid War (weird but fun game – I haven't tried multiplayer yet), Warzone 2100 (it's like Command and Conquer), Open Arena (like Quake Arena), and Foobilliard.
Just this week I read somewhere about the Doom creators (Id software) releasing some code to the open source community. I suspect there will be some crazy open source FPS apps coming out soon after…
Whether you can completely switch or not, these are some open source replacements for proprietary aplications you might be currently running.