Here's a game, Keyboad Climber, that I have used with both 1st and 2nd graders to help them with letter location and hand placement on the keyboard.
To play the game, students need to help the monkey jump from tree to tree by typing in the letter shown on each tree. If the tree is on the right, they should use their right hand and if the letter is on the left, the should use their left hand. If they press the wrong letter, the monkey drops back down to the bottom and you start again. The monkey also goes back to the beginning if you take too long to find the correct key.
There are several levels which keeps the kids interested as they go. My kids loved level 3 when the monkey is in space and is wearing a space helmet.
The main site, http://www.tvokids.com/ has lots of other fun things to explore as well, including math and science games, arts and music, puzzles and games, and more.