I’d recommend DrawIt Lite, that’s vector-based graphics program (typically well-suited for page layout and design projects). It’s fully featured, easy to pickup, and powerful. There’s a Pro version available that’s $40 but if you’re looking to do a few simple projects the Lite version should suffice. Two other programs that are predominantly raster-based (which means they’re better at dealing in photos and working with images rather than layouts) but very highly regarded are Acorn ($50) and Pixelmator ($59) but I didn’t suggest them because DrawIt is better suited for design projects and they have free trials but not an actually free version. An exhaustively well-written comparative review of the three programs is available here. A good read even if you’re not interested in the programs themselves but about how 3 programs can approach the same function in radically different ways. You can also look at this About.com listing of free graphics software for the Mac but I doubt you’d find something better than the above.