Kayaking and other outdoor activities are great if you're dating someone who's athletic. If your city has a large body of water nearby, Kayak rentals can go for $10-$15 an hour and you can see neat stuff. Lots of schools with aquatic athletic programs like crew will also offer student discounts too. I've also taken a few girls who were interested in rock climbing to a bouldering gym.
My husband and I have LEGO dates. We buy a set and build it while watching a movie or tv show (one we've seen so we know what's going on while we build) and usually booze.
Ice skating. Especially if you have a rink that also has a bar.
Aquarium, Zoo, or Museum
Something that get's you walking and gives you a lot to talk about so if the conversation lags you can pick it up easily.
Go to a planetarium. Reasons:
- Usually either a very cheap or free experience.
- Reclining and watching the stars.