RHK
This is an applet I wrote when I was fifteen and a senior in highschool (Type "help" into one of the fields to see the date). The source is fairly clean, but not well commented. There are certainly some convoluted things about it, but I like the finished product. Type in a series of bases (letters 'A', 'T', 'C' and 'G' for DNA, or 'A', 'U', 'C' and 'G' for RNA) to see how they would be translated in a cell. Of course, this is very, very simplified. It doesn't do excisions of introns, etc. But all that stuff is species dependent, anyway. Try it out.