I use the following on my computers to help me prep and run games:
eTools from
www.codemonkeypublishing.com (no longer for sale) -- despite its flaws it is crucial to the way I prep and run my games. I use it to create stats for my own PCs, as well as my NPCs and monsters, advanced monsters, and templated monsters. One of its hidden benefits is that I get to see the rules from various sources "folded in" to the core rules. I can look at a master list of feats. I can look at a master list of spells. It helps me integrate information from new purchases. I have tweaked the stat block and character sheet files so I have them the way I like them. That took me a long time and a lot of trial and error.
Auto-calculating spellsheets and spell generators (look around in the Downloads area of EN World for some of these) -- I have used 3.5 versions of Steve's Excel Spellsheet for a long time, and still rely on them heavily. Likewise with Expanded Psionic Handbook power sheets. However, I have not updated these resources in some time, and thus they become less valuable when I want to use spells from a source not already in the sheet. They are a pain to update, frankly. Lately I have been relying more on SpellGen
http://d20spellbook.home.comcast.net/ -- to prep PDFs of spellsheets, particularly if I'm using something from the Spell Compendium. For me, having pre-caluclated spell stats (DCs, damage, ranges, etc.) makes NPC spell prep a breeze, and running NPC spellcasters in combat is a no-brainer when I don't have to do math in my head.
http://d20srd.org/ -- I'm sure you all know about this resource. The searchability, the monster filtering, the dice bag, and the dice rolling mechanism built into the monster stats make this a superior reference. This plus wireless laptop = all the rules at my fingertips.
PDFs -- I am a fairly recent PDF convert. Even if you're not into buying them, there's no reason you can't go to
www.paizo.com and download their freebies. The maps alone are worth it.
Phineas Crow's maps -- An EN World poster created about 100 maps of different kinds of locations and bundled them together for downloading. I don't have a link handy, but that resource is going to be really helpful when I start running more free-form campaigns.
FR Interactive Atlas -- An oldy but a goody -- I use this thing all the time in FR games to measure distances, make close-up maps, and for scads of cities, towns, buildings and dungeons I can re-use in other games.
Excel & Word -- pretty obvious, but worth mentioning. I've been using Excel, in particular, to keep track of the campaign calendar for my Red Hand of Doom game, and it works pretty slick. I can move scheduled events around easily, track the PCs actions, etc. Word, of course, is for typing up my adventure notes, copying/pasting eTools stats and the calculated spell info, adding illustrations, and creating player handouts. I use the hyperlink tool in Word to make links to PDFs and other documents that don't really integrate right into the page in a Word document.
WotC Website --
www.wizards.com/dnd for lots of downloadable maps and illustrations. An incredible resource, I visit it a few times a month to keep up with what's new.
Personal forums, personal websites, & Yahoo groups -- I don't have one myself, but one of my DMs has a forum for his game and it's handy. Another uses a Yahoo group, which is even handier -- the messages get e-mailed, but they also get archived, and you can post files and links, making it a great campaign storage site. I post my own campaign stuff on my personal website -- including illustrated guides and campaign logs -- for my players to read and use.
A special note about campaign logs -- they are well worth the effort to maintain. They help during the campaign by giving the players something to refresh their memories between games, and then after the campaign they help you remember the great times you had playing. You can bribe your players into helping you do it by giving little XP bonuses, action points/hero points, etc. if necessary.
