African dwarf frogs are fine. Make sure they're not actually African clawed frogs though. And they can be hard to feed. Always keep in mind that you're betta may be aggressive towards them and have a plan B.
Newts? never heard that asked. I wouldn't do it. It would be very difficult to get a good water/land ratio to satisfy both species. Not made easier by the fact that newts need very shallow water. Also, one of the foods that newts eat include small fish. Even though a betta is probably too big, that will in no way guarantee that it won't go after the betta. And bettas are slow movers and would make an easy catch. Also, newts require a cooler temperature than bettas. It seems just all around incompatible, not feasible and a bad idea to me.
Last edited by SmokeNLark; 10-03-2011 at 12:01 PM.