Which seats will work best for three across?

There's a relatively new seat on the market, it's called the Diono Radian. It's made for smaller vehicles, as well as for three across. It goes rear-facing and forward-facing and has really great reviews. It's awesome for space! The only thing is, it's a little pricey. If you can afford it, I highly recommend that one.

Otherwise, more brands are coming out with space-friendly carseats. Safety 1st just came out with their "Guide 65", which is rated for smaller vehicles/3 across, and Eddie Bauer has their "Sport". I'm not sure what's available in the states, but all three carseats I mentioned are great seats, the Safety 1st Guide 65 being my favourite.