It's always good to have a few graphics design tools around, to do the odd bit of work on pictures or just for fun.
There is a few freeware I would like to recommend.
Editor Rating: 8/10 - Highly recommended!
With the Gimp, you get for free what you would pay hundreds of dollars in a commercial application. This is one really capable graphic application with support for layers, masks, filters, special effects, curves... We are talking the real deal here. It's however not really easy to use, even if you are already somewhat familiar with apps like Photoshop or Corel. But hey, Photoshop/Corel aren't easy to use either, otherwise, there wouldn't be a quazillion "HowTo" books in any library you care to visit.
Editor Rating: 7/10 - Recommended!
You never heard of Inkscape? Surprisingly few people have and yet it's an excellent free vector-based graphic design application with many of the tools you expect from commercial-grade vector design including layers, objects, effects, grouping, transparencies... Not only that but it's darn simple to use. While it may not fully satisfy the needs of a pro, it will sure go a long way for most of us.
Editor Rating: 9/10 - Highly recommended!
Yeah, Google did it again! Once installed, Picassa will locate all the picture files on your disk and create a complete, fully searcheable album of all your pictures (you can choose to exclude locations to avoid getting pictures you are not interested in - like picture files that comes with your documentation). Picassa can display them as a slideshow, batch rename pictures, keep track of your favorite pics, apply basic fixes to fix common problems like red eyes, constrast and lighting, crop... and they work just great. There are also some slightly more advanced fixes you can apply in a jiffy. You can take a somewhat dull picture and make it look great in a couple clicks. Better yet, you can apply fixes on batch mode. Suppose your camera settings were a little off, and all the pictures you took are too dark. A couple tries, 3-4 clicks and hop, hundreds of pictures fixed, all in one shot! And it doesn't stop there - this review does however. ;-)
Please contact me if you wish to suggest another tool in this section.