Does the weave have something like this? Where prospect DM's are taught how to DM by experienced ones?

If so where can I sign up?

If not why don't we?

There is one in the works at this point, but it's nowhere near ready to go. Right now, your best bet is to ask questions when you need help with specific things, and you're in the right place to do that.

Also, a DM Guide, we have one.

I get the basics of it all and have been DMing 3.5 for a few years now I just want to have an environment to improve.
Should I just offer to Co-DM for some one?

That's one option. Another is to ask for a mentor co-GM. That would be someone who's paying attention to the game and can offer advice or answer questions, make suggestions, that kind of thing. Then you have the option of jumping into the deep end of the pool.

My general advice for the majority of people is to get yourself into a game as a player first, even if you've been tabletop GMing for years. This is because PbP is a different animal than tabletop, and seeing it as a player means you're only worrying about the one character while you get the hang of the pace and whatnot specific to the format.

Personally, I'd been gaming for about 15 years, roughly 12 of it as a GM, when I got into PbP. I played for about three months before I decided to give a shot at running one myself. The few months spent as a player showed me the major differences, got me accustomed to the format, and generally made it possible for my first game to not be an utter flop (it lasted not quite a year).

Alright I think I know what I will do know, thanks for the answers. Time to hunt for a game!

Another option is to view the reader guide (also listed in the MW GUIDES which are all linked in my signature) and find a game on there from one of the long standing games and join up as a reader and then keep in regular communication with the GM by asking questions and such and trying to understand their methodology. It would also help to tell them you're not just looking to learn the system, but how to be a GM.

The reason I suggest this is because it may seem odd to ask to be a co-GM out of the blue, but readers are generally accepted by non-private types.

When selecting a game to view as a reader or CO-GM, make sure it's at least 3 months old, preferably a year or more.