A broom and dustpan! Kidding. Seriously though, have then help you around the house. Make it fun sounding and you get help, you spend time together bonding, it keeps them entertained, and they're happy and proud to help mom/dad.

For actual toys, Lego makes oversized blocks called Duplos. Lego's site mentions children as young as 1 1/2 enjoying them. At that age, the Duplos are more like blocks to knock over, but they're still fun, safe, and encourage creativity.

My 2 1/2 yr old son is fond of jigsaw puzzles, duplo, train sets (Brio-type wooden ones are easy to put together and take apart), baby dolls (preferably if they cry when you squeeze them) with accessories (clothes, plates and cutlery, pushchair), and lots of other things so long as someone will play with them with him.

Answers to this similar question may provide some help http://moms4mom.com/questions/1561/age-appropriate-toys

I read the Baby Cheapskate blog, and they recently had a post talking about the most played with toys for ages 2.5-4. Perhaps some of these would work for your son?

My 2.5 year old son has had a lot of fun playing "Memory." His attention span isn't always long enough, but if we play with a small number of cards (12 is normally the limit) he loves trying to find matches.

His other favorite toy is a set of play tools, he takes his hammer and screwdriver and "fixes" things all over the house. It's not capital-E Educational, but I think it's helping him learn a lot of things.

He's also very interested in using the computer now. We started him off with baby smash and he's since mastered a touch pad and loves playing online games from PBS Kids, Nick Jr., and Playhouse Disney.

In addition to Tammys recommendation, I think this question "Learning the abcs" has some answers that could be of interest to you as well as some of the answers to the question "Teaching your child to read"

Letters and numbers, in both wooden form and magnetic, picture cards, memory cards and stacking toys and puzzles from the EDUCA range were my favourites when my daughter was around two.

I have to admit that I was a bit biased against all the "strong marketing" for toys that were made to look like "must have educational toys".

EDIT: I had completely forgotten about Lego its wonderful.

My kids really liked the Leap Frog Fridge magnets, coloring books and flash cards. Can't forget Hot Wheel cars! The cars are sooo cheap and they last for YEARS! Wooden blocks are great too and my 4 1/2 still plays them.