can anyone recommend a great hamster cage?

Hate to tell you, but you won't find a connectable cage that's big enough. They simply do not make them. Commercial hamster cages (Crittertrails, Habitrails, etc.) are not designed to be good homes for hamsters. They're designed to be fun, colorful toys for children. It's the same as the commercial rabbit cages that are way too small for a bunny.

The minimum cage size for a single hamster is 30" x 12" (360 square inches of space). The cage you posted is about 1/3 of that size.

Aquariums actually make perfectly suitable homes for hamsters. The whole issue of being bad because they don't have enough ventilation is a myth (as far as hamsters go). Ventilation is only an issue when the animal kept in the aquarium produces a lot of urine. Aquariums are unsuitable for larger rodents like rats, guinea pigs, etc. However, hamsters are small desert-dwelling animals that produce very little urine. Therefore, they can live quite comfortably in an aquarium. As long as you do frequent cleaning, it would be fine.

In fact, many serious hamster keepers use aquariums because they're one of the few ways that a hamster can get adequate space. A 20-gallon long would be the minimum size, but a 30- or 40-gallon works much better.

If you didn't want to do an aquarium, though, you could go with a bin cage. Bin cages are basically converted storage bins, with the lids replaced with 1/4" wire mesh. Images for ideas: https://www.google.com/search?q=hamster+bin+cage&s... They're cheaper than aquariums, but require some DIY work.

ETA: A 30-gallon tank is a good size for a hamster. A 30-gallon would measure 36" long x 18" wide, making it 648 square inches. It's almost 300 square inches over the minimum 360, so it's a good size. A 40-gallon is the same floor space, but about 6" taller (which is good if you have a Syrian hamster that needs a big wheel).

That rabbit cage would make a perfectly fine hamster cage if you covered the bars with mesh of some sort. That's not something I've ever done myself, so I'm not personally familiar with it, but I know it's something that can be done.

The Hamster Hideout forums are the best I've come across regarding hamster care.

Really Cool Hamster Cages

Yes, ventilation is just fine for hamsters in tanks. The problem with rats, rabbits, guinea pigs, and other bigger "small" pets is that they produce more urine than hamsters, gerbils, and mice. So, ammonia builds up quickly in tanks. This isn't a problem in smaller rodents as long as you keep the tank clean. Regular cleaning weekly to bi-weekly, spot cleaning daily. Since you have bunnies, I'm sure you're used to such routines, though. :)

Thirty gallons is perfect. The recommended size is 20 gallons. That's literally JUST big enough. However, since hamsters are very active runners, they need as much space as you can give them. Seriously, they can rule several miles a night in the wild in their hunt for food and other resources. I think a hamster would be VERY happy with thirty gallons. If you can get bigger, even better. I do have to suggest bin cages, though. If your rabbits have c&c cages, I'm sure you're no beginner to DIY! Bin cages can look quite bulky, but are cheaper than tanks for the same amount of space. A guide is here: http://www.instructables.com/id/Hamster-Bin-Cage-T... They are, also, stackable. You can, also, look into detolf cages. Also cheaper than tanks (as you get a LOT of space without having to connect several tanks) and DIY. More here: http://hamsterhideout.com/forum/index.php?showtopi... Detolfs can be bought from IKEA. The bunny cage is definitely big enough (at 698 square inches) but would require meshing on both the inside and the out (to be extra safe).

As far as good hamster forums goes, I love hamsterhideout.com. Very friendly community, very helpful members, and very informative. hamstercentral.com is a good hamster community, too. I am an active member of both of them and definitely recommend them for a new hamster owner.

Good luck!

I wouldn't recommend cages with tubes, as many times the tubes are hard to clean, and I have had hamsters that would be able to chew their way out of the tubes, usually where they would connect to the cage.

You could even make your own C&C cage for a hamster. Just add smaller wire mesh to the panels. This would provide for plenty of ventilation, allow as much room as you would like to give your hamster, and be escape proof if made properly. Instead of using chewable plastic zip-ties, use a thick wire tie to join the panels. I've seen several C&C cages made for hamsters and have heard good reviews of the cages. Most cages that they make for hamsters are way too small for anything to live in.

If you don't wish to make another C&C cage, you can get a large "bunny" cage (you know, the kind that says they're for bunnies, but are in fact way too small for a bunny to be happy in) and add the smaller wire mesh to that cage.

Critter trail and Jackeroo are superb brands. Here is the object, the are 30 bucks, and all Crittertrail and Jackeroo's come with tubes. That you could add on tubes for about 10 bucks. Forty bucks. Its low cost, in comparison with the 80 dollar one you noticed! Excellent luck with the Hamster!

It's a great question

DO NOT GET A HAMSTER, THEY ARE EVIL! NO JOKE!