Currently, I’m using the iPad — 10″ screen is big enough to read notes and it’ll swap between my notes (usually on Dropbox), a pdf reader for game books or character sheets, and the dice program (Diceshaker, in this case.) Battery life is robust enough for a long session (hell, I got from Edinburgh to Albuquerque on a single charge, using it the whole 15 hours.)

I myself use Timpani (here) for SRD 3.5 gaming, but it does require a version of Excel that handles MSBasic programing (i.e. it won’t run on OpenOffice).

I haven’t DM’d in a while, but my experience is that it can work for you. Our group’s last couple of DM have used their laptops extensively. The biggest problem for one of them has been placement versus player interaction. He is DMing for the first time, and it’s taken a while for him to get the hang of setting up his laptop so he is facing the players most of the time, instead of having his back turned to them.

Also, I’ve found the whole “PDF” thing is overrated. Players can find stuff in a book infinitely faster than a computer can, even with the search function. Usually, the search function comes back with so many hits to sort through that by the time you have, the player has found the thing he needs to reference before you can get to the item you want from the search function.

For my upcoming Traveller game I am thinking about building an old laptop in to a web/ DNS server so I can have an “internet in a bubble” at the table. The idea is that all the important game data is on the server and the players can “log in” via the ships connection to the net. Though this game type would require all players to bring in a laptop.

Also, Obsidian Portal is the bee’s knees for Wiki and Institutional Memory.

If players starts talking about a spell I haven’t prepared for, I can look it up without them even knowing. And I can do it quickly. I can also stack up a load of spells and monsters that I might be about to use.

Even if you’re not using a site like d20srd.org, I’d still advocate them for note taking, combat tracking, die rolling etc.

I use a 15″ laptop and find it is no more an obstacle than a DM screen. In fact it’s normally less of an obstacle. With smaller laptops coming out all the time that can only get better.

Having said that there is nothing better than a real life book for having a read. PDFs do not replace core rule books IMO for being able to read them out of the game as you try and become familiar with the rules. Laptops come into their own as when they speed up rule finding and therefore increase the fluidity of the game. At that point, you almost forget they’re there.

Aside from that, I’ll usually have up .pdf rulebooks and all the baddies’ character sheets.

I’m DMing without a laptop at the moment, and finding it really enjoyable. There’s something about rifling through papers, or cracking open a book – I know as a player, one thing that always gets my attention is when the GM digs out some big book from halfway down the stack.

Some things are harder, and some things are easier. If my laptop wasn’t a gigantic monstrousity, I’d probably bring it along, if only to have a couple websites up, and a notepad file for things like initiative that I have to erase and rewrite frequently.

That said, I think that GMs get a lot more out of laptops than players. They also have fewer temptations and distractions, as a GM always has to be “on stage”.

As I mentioned, I GM off of a 15.4″ widescreen laptop with 1920×1200 resolution; I can fit view two full sheets of ‘paper’ side by side on it. I was going to sell this laptop, but kept it strictly for GMins. For playing, I’m currently using a 13.3″ with 1280×800 resolution; I can’t even see an entire character sheet on it, so it’s pretty frustrating. But there’s not enough room at the table to go with the 15.4″ laptop, so I may actually go with paper and cards (it’s a 4E game).

Another option, that I left out mainly because of my inexperience with them, is a tablet PC. I’ve seen players with tablet PCs which display a character sheet perfectly. That said, if the software isn’t there to support it, you’re just using a thick and expensive piece of paper…

Your right about Wikis becoming a standard tool. The hardest thing about them, is finding one that’s right for you. One of the more interesting one I’ve found is http://www.tiddlywiki.com/ . It is a single file Wiki that uses JavaScript to handle adding and deletion of data. It’s single file nature means its something a normal GM have on his laptop without an Internet connection.

The Hypertext D20 SRD is an excellent site, if you run a DnD 3.5ed game. There are few others like it, such as http://www.systemreferencedocuments.org/35/sovelior_sage/home.html (which has a version you can download)

PDFs are nice. I know I’ve paid good money to get a PDF of a book I already own. Which is why, I tend to buy Paizo stuff direct, nothing like a free PDF version with your printed book order. I wish there was a way to prove you brought a book and then go to a website and get the PDF version.