I used to DM D&D 3.5 and Pathfinder, but have long since decided it just isn't my cup of tea. However, I used to be big into play by post for that sort of thing.

Here are my suggestions to you:

[list][*]Try looking in the Tabletop Roleplaying section, first. You may have better luck there.
[*]If that fails, try the Paizo forums. They have sections devoted to play by post games.
[*]Finally, you may consider the Giant in the Playground forums, though that's a dangerous place to tread.
[*]If the last two options don't sound appealing to you, you may consider trying out other tabletop games on these forums. I've seen people push a huge variety of stuff over there, though I haven't dived in myself.[/list]

Happy hunting! I hope you get the Pathfinder or 3.5 experience you're looking for.