The USGS Water Science School
Here is a certificate of completion that you can print out. It will look best when printed on a color printer, but it will come out fine on a regular black&white printer. Of course, it is suitable for framing (if you supply the frame!).
Depending on your browser program and printer, the certificate may or may not print properly (an edge might get cut off). I'd suggest first trying this horizontal version of the certificate. If it gets cut off when you print it then try this vertical version.