Offense and Defense are capped at level x 5. All other non-tradeskill skills are capped at (level + 1) x 5. Tradeskills have no cap except that you can only get one above 200 without AA's (I think), with the exception of Research which is capped at (level - 15) x 5. This is all from memory, but I am pretty sure it is correct.
Caster's Realm has a list of all the skills for each class and their maximum values, both pre- and post-50. Actually, I just put the Skill list into my Storyline folder so I can view the maximums in-game. You can download Storyline text files from most of the UI interface websites, especially http://www.eqinterface.com/ . I highly recommend them, especially if you only have one computer available when you play.
Game on,
The Oneiromancer