The very earliest days of the PC revolution were soaked in idealism. People shared their knowledge with one another freely; the very idea of charging for software was an anathema. The early days of the Internet had a similar rosy view of the world.

Today, of course, all that has changed. But there are still plenty of idealists out there, sharing their work with the world freely, and asking others to work cooperatively with them. That's the underlying idea behind the open-source movement. People create software, and allow others to download and use it freely, and let them modify it as well.

This idealism can create great software. That's where Firefox got its start, for example. But there's plenty of great, free open source software beyond Firefox. I've rounded up 20 of my top open-source favorites. Their sophistication and power will surprise you; you'll find everything from a universal instant messaging program to powerful multimedia and graphics tools, security software, and beyond. The programs show that open source adherents aren't wild-eyed zealots -- they produce plenty of great software.

Graphics

Gimpshop

Open-source software has never been known for its photo processing prowess. Until now, that is. Gimpshop is an exceedingly powerful Photoshop look-alike that has far more features than you, or most people you know, will ever use.

If you're looking to do something as simple as touch up photos, or something far more sophisticated, like work in multiple layers, it has the tools you need. There are also numerous effects and filters, the ability to easily create color gradients, and plenty more. In fact, if all you want to do is basic photo-retouching, it's probably overkill.

But if you want to indulge your inner artist, there's plenty. The program is based on a long-time open source favorite, GIMP, but has more fit and polish, and a Photoshop-like identity.

Inkscape

If you're looking for a graphics program that lets you create illustrations and graphics, much like Freehand or Illustrator, then give Inkscape a whirl.

It includes a surprisingly powerful set of tools for creating graphics from scratch, or for editing existing graphics or photographs. You'll find numerous drawing tools, the ability to create layers and combine them, and more.

The program supports the standard Scalable Vector Graphics (SVG) file format, as well as many others. It imports files from many formats, including .jpg, .png, .tif and others, and exports to numerous vector-based formats and .png.