http://pacificcoast.net/~gthompson/There's a free tax program, and you can do them for previous years as well. Download the 2006 version 1.1 and then update 1.2 on top of it. Do your taxes and print them, and mail them in.
If you're worried about the dead trees, there are online NETFILE type websites. But I think this way is probably the simplest if you're used to printing the forms and signing them.
You're not obligated to print the forms, so you can just punch them in to see what you'd get back as a refund, or have to pay - and then you can go EFILE or something.