Prizes, ebooks, gift certificates, etc. yeah. The other key is to present people with lots of offers. The idea is that if you present someone with 10 offers they will pick the one they are most interested in. Overall, this produces a much higher quality lead for the advertiser vs. just showing someone 1 offer and telling them you'll pay them $10 to do it.
Most quality name-brand offers are slowly not allowing cash incentivization. I think soon the only ones that will still allow it are the borderline "scam" offers that make a lot of money via their confusing terms and conditions, borderline illegal billing practices, etc. And I wouldn't base a site or business around these, because they could disappear at any time.