I keep one White's Tree Frog and agree with Don all the way. Though they're not very active animals, sometimes even at night mine will just sit and sit and sit, they have wonderful personalities and are great for beginning frog owners (not sure if you said you've kept frogs before) because of their durability. They're especially a treat when they're small and can't hurt the plants in your viv, but White's can get up to 5' in length, and trust me, that's HUGE in the frog world. XD

I haven't had experience with any other frogs (and I haven't even had Bruce for three months yet) but I can assure they're a wonderful pet.

The other frogs I'm excited about, and looking to own sometime within the next few weeks, are Phyllomedusa, as mentioned above. Monkey frogs are GORGEOUS and all of them have distinct looks. I find these particular frogs fascinating because of the way they move and how closely they can resemble their name sake. My favorite of the Phyllomedusa (though keep in mind I've never kept one but have done extensive research) are the P. Tomopterna, P. Hypochondralis, and P. Bicolor. They are absolutely fascinating, to me anyway.

But yes, sadly both of these types are nocturnal so if you want frogs for viewing it would probably be best to go with Dart Frogs as the others have said.

Sorry about being a total n00b giving my two cents, I'm just trying to be helpful. ><