Yes, but it depends. It seems AIM for the Sidekick is the best, from what I've gathered and experienced. The free ones for the Treo have a few drawbacks. I used Toccer, and it works ok, but there are plenty of others out there. Some are free, other cost money and obviously have more features. go to www.howardforums.com then go to the Palm/Treo section. Search for AIM or instant messaging then read to decide which one suits you best.