There are a few good sites for ECW miniatures. The best, in my opinion, is Auldearn 1644, but the author took a year off, and hasn't started back up.
http://auldearn1645.blogspot.com/
I've done a bit of basic converting with a regiment of cavalry, using royalist cav to build the lancers. It was my first working with green stuff- something I've always wanted to try but do it because of what I've read on this site.
I also made bonnets and a few plaids for the third regiment.