More info:

It's definitely oil... We disconnected the vacuum line from the transmission to discount the possibility of transmission fluid and after a few minutes of running there was a small puddle of oil beneath the exhaust pipe. *sigh*

Also, I forgot to mention:

1.) This was an abrupt problem... Literally, it was running fine and then one morning it just started smoking.

2.) While test-driving it, I've noticed it's losing power, especially on hills.

I'm guessing this would suggest bad rings? I really can't afford to rebuild the engine at this point... Is there anything else I can check?