You thought 3d was good? Coming soon the Team17 Worms 3d landscape editor. The Teamies have stated on a few sites thet the editor will be released on their site shortly after the release of the game, so hopefully not long now.

There's still no sign of it on the site, but hopefully it's not far off. Untill then you'll have to trawl through the Team17 forums for interesting land codes to play on.