If you like the phil and teds style the Hauck Freerider is v similar with solid tyres and a small price tag.. which I would very much assume will mean lesser quality, probably less features etc. but can't say for sure as have only seen one on a display stand that no one was allowed to touch.
Otherwise hmm what is there,
B Dual - nice to push, pretty wide though, esp when you have to put the wheelguards on and the kids are sometimes a bit slumpy in it but not always. Good all rounder, decent quality.
Oyster Max - think has air tyres and isn't out until 2013 but would have to check.
Jane Twone - very good to push but seats v close together and lower one is LOW so child loading is an issue. I also think the rrp is very steep tbh (I have one and love it but not without being able to see the downsides!)
Smyths Toys Dimples Duo - pretty good for the £250 price tag (can often get for 200 I keep seeing stuff about 20% off days etc.) especially being able to have the baby face you and the toddler face forwards, it's a bit large 66cm wide and 106-122 long depending on how the seats are but generally pretty good as long as you're not expecting anything fancy!
If your toddler doesn't sleep maybe and Uppababy Vista with Rumble Seat.
Micralite twofold is coming soon but I think that has air tyres at the rear if not the front too, I'm trying to stick with solid tyre suggestions! I would also mention the Mountain Buggy +one in this accidental air tyre breath...
Think I've run out now 
Obviously also lots of other front and back type tandems - gracos, safety 1st etc. It all depends on your budget and needs really, there isn't a massive choice of good tandems imho.