astro.com is a fantastic site, I've used it LOTS in the past. A tip for posting natal charts - you need to save them to your computer, upload to a server (if you have a MySpace or Facebook, or any other sort of account where you can upload pics then any of those should be fine), and then link to it. That way you can permanently post it.
Also, it's been found before that if you have an astro.com account and try to link directly to the charts, people can access your account. So saving, uploading to somewhere else and then linking is the safest way to go!