I agree with Cheri. Reed frogs are great jumpers and often fearless, so you need to have a secure lid and be prepared for some action when you remove the lid Last year, I had the opportunity to care for 400 Madagascar reed frogs for the zoo I worked at. They were getting ready for a new exhibit. I had to clean the cages every day. When the lid was opened, the frogs jumped all over the place and even a few jumped into my uniform shirt, what excitement! Make sure you have no holes in your lid or terrarium, they are great escape artists too. Also, for some reason their poo likes to cling to the walls and very difficult to remove, not sure why. These are great frogs and easy to care for and breed. Some species that I recommend are:

Heterixalus alboguttatus and H. madagascariensis (Madagascar species)
Afrixalus fornasinii (African greater leaf folding frog)
Hyperolius marmoratus (African painted reed frog), there are 10 subspecies, each with their own color and pattern, awesome!!

These species should be fairly easy to find.

If you are interested in a totally different kind of small, easy to care for frog, I recommend any frog in the genus Scaphiophryne (Madagascar rain frogs).