This is a page with links I've found that are helpful. If you find a helpful link or site add it to the wiki, help your fellow DM's out by making this an easy to use reference page, and if you can think of more topics by all means add them! (I_smile_alot)
- [www.pathguy.com/cg4.htm] A good character generator for 3.5, that generator is a little more refined. just have a decent connection, because its a big page. Good hunting
Official Downloadable Adventures
-  Test Drive D&D, WotC's download links for the quick-start rules, H1 Keep on the Shadowfell, and Khybers Harvest.
- Masterplan Excellent tool for designing and running your 4e adventures/campaigns, they also have links for some very good video tutorials on their site.
- Rolld20 An alternative to the VTT which can be used solo or within a google+ hangout.
- DM Tools A resource for pathfinder and 3.5 games when you need to put together an adventure on the fly.
3-D Paper Buildings
- Useful Links for DM's This is a huge list of links, a few of the links no longer work but overall you'll find it a valuable resource
- Official Campaigns This is actually the wiki for DnD Insider, it has campaigns cataloged by adventure and is updated as they're added.
- Glossary of gaming terms The glossary will help you familiarize yourself with many of the terms and acronyms tossed about the forums. I started it on pg 29 which is where it currently starts but it'll start on the last page no matter how long it gets. The first entry is also indexed & hyperlinked which I found very helpful.
-  This is most definitely not a site for free stuff, although they do offer free material from time to time. What it is is a very reliable source for a huge amount of downloadable source material at reasonable prices.
- Obsidian Portal Used by many DM's and players to track session notes, characters and treasure, obsidian portal is a free resource. They do have a subscription that adds a few more features but everything you really need is free.
Online sites for buying stuff
I know that there are lots more, I just listed the 3 I've made purchases from and know about.
Other sites with good articles and some resources
- Sly Flourish This is one of the better known sites with a number of good articles and some resources, they do publish some of their own material so you'll see a bit of self promotion but it's not excessive and the material is solid as well as usually inexpensive, as well as some material that's offered free.
Most Valuable Resource
OTHER DM's, talk to your fellow DM's, network, most of all have fun, and as always, Happy Gaming! So, be a friend to your fellow DM's and when you find a helpful, tool, trick or resource add it to the wiki!