What are some of the best educational toys for a 2 1/2 year old?

Puzzles. My 3 yo loves them, and so we bought a bunch with cars and such on them. I would go ahead and get some of the more difficult ones (12 piece jigsaw). They figure them out so quickly!

Edison from Leap Frog - loud but worth it

Just looked it up - it's actually called "Alphabet Pal"

Books and puzzles. Especially ones that mom and dad do with them.

A ball. I think it's great to teach a child of any age. It is what I used to teach my grandsons about Newton's Law of Motion but at your son's age it could be so much more. He can learn to entertain himself with it or to play with you or others with it. If you get one with abc's and/or numbers on it you can work with him on alphabet or numbers. You can also teach him coordination and manual dexterity. You can teach a child so much with something so simple and it's always affordable.

We bought our daughter the Fisher Price Fun-2-Learn Color Flash Laptop for her 2nd birthday. Only 2 months later and she not only could sing the whole alphabet song(she'd been doing that since 18 months old) but she knew what sound each letter made and could find them in a second on the computer. Also, she knows lower case and upper case letters and can use a mouse now. The laptop teaches about numbers and has a couple of games too. So any laptop like this one would be good. I think there are some that also teach about shapes and colors. Anyway, I think it was the best thing we ever bought for her. The best part is that she loves playing with it and we love that she's learning while playing.