As always, your suggestions and questions are welcome. Questions for next week should be left in the comments. When asking a question please include which machine you're running and which version of Mac OS X (we'll assume you're running Snow Leopard on an Intel Mac if you don't specify). And now, on to the questions.
I don't have the money for something like Adobe Photoshop. What's the best, cheaper alternative?
For my money, the best Photoshop alternative at the moment, and one I use every day, is Pixelmator. It has many of the same features as Photoshop like layers, masks, level and curve adjustments and a whole lot more. Plus, it's a relatively simple program to use and is written to take advantage of your Mac's GPU when doing image processing.
It also supports most image file formats including Photoshop PSD files and has many useful Automator actions built in. Actually, because Pixelmator is such a good app and takes care of most of my needs, it's pretty rare that I ever open Photoshop anymore. Sadly, Pixelmator is not free, but at US$59.00, it's a heck of a lot cheaper than Photoshop.
Some other alternatives include the open source GIMP and its more Photoshop-like cousin GIMPShop. You can also check out Acorn, or if you need very minimal tools like crop and resize, ImageWell. Of course, Apple's built-in Preview.app can handle many of these low-end tasks as well.