How about op. 26? That, to me, is one of Beethoven's most interesting early piano works (well, I'm sure many would agree as well). He starts out with theme-and-variations, goes into scherzo, then funeral march, and finally an allegro section, not unlike a symphony (or op. 7 for that matter, somewhat). There is some wonderful music in there as well.
I also will throw out op. 14, either one. I recently heard the first sonata of that opus completely butchered by an unfortunately unconfident girl at my school, but if pulled off correctly it would be tremendous. I personally favor the second one, however, and I really don't think anyone could be bored at all by any of its three movements--plus, it's easy but not too easy! A great Beethoven introduction, I'm sure.
And there is always op. 27 no. 1, which was my own first sonata. That could be a little tricky--it took me close to a year (but at the time I was 50x crappier than I am now, and I'm sure you're not nearly as bad as I was then)--but it's certainly rewarding.