[tsahyt]

Writing a toy ray tracer is something that I'd recommend to everyone who's interesting in becoming a better programmer. Once you get deep enough into it you'll encounter so many interesting problems (e.g. data structures, software architecture, some linear algebra, etc.) to hone your skills on. It's almost up there with "write your own compiler" as a learning experience in my opinion and you get the added benefit of creating some pretty pictures in the process.