I haven't had a piano lesson in about a year or a year and a half, and I'm looking to really start playing again.

I want a song that I need to work on, but one that isn't completely over my head.

The last things that I really played (this would make it about two years ago) were Moonlight Sonata, Solfeggieto, Mozart's Turkish March, and a Minuet of Beethoven (Opus 49, number 2?).

I've picked these songs up (and a few others) that I used to be able to play pretty well and I've got them under my fingers again. Now what songs are out there for me to learn that are a bit more difficult than these?

If i were you i would choose Chopin's etude called "Revolutionary". i dont know the opus number, sorry.

I've played around with that piece a few times.

Would that be too over my head? It seems like it would be to me, but is that normal?

Song, not piece

A song would be something for voice, or at least a something for piano/voice

Take a look at Mozart's other Sonatas. K.545 is popular and not hard. Take a look into some of Chopin easier preludes, as well as his Nocturnes.
Op.9 No.2 comes to mind, and it would suit you well. It's too easy - I'm sure it's going to get you busy. You should also take Op.37 No.1 into consideration. Wonderful melody.

You idiot...

I think you should do some Bach Inventions and a Mozart Sonata or two. Not sure which ones to recommend.