Two things worth "seconding" here:
1. Check out Necro's site for downloads. A lot of their extras and web-only stuff is really, really, really useful and cool, and expands on stuff that you really want to work into the adventures.
2. Although Dungeon Crawl Classics are indeed Goodman Games and not Necro, several are worth looking at, too. Vault of the Dragon Kings, Crypt of the Devil-Lich, the adventure about the Asylum (can't recall the name) and especially Castle Whiterock are all FANTASTIC! Castle Whiterock has to be one of the best mega-dungeon/sandbox sets I've ever seen. Incredibly well written, internally very consistent, excellent design work, excellent production values, and really, really good scripting in order to keep everything manageable. You can pretty much open up any part of any of the books and just go. Considering how freakin' huge this project is, that's awesome.
Tons of RP and quests (just before 4e came out!) and neat design.