executablesNotepad: what it says on the filename.
AIM Chat: Primarily because we all have AIM, but also because it's the easiest to use for any special font stuff. It's even got a built-in die roller!
Trillian: combining IRC and AIM means we've got more options in case a player has trouble connecting to one or the other. Also, on my end I have a homogenized format for IC/OOC/personal IM logs when going over the events of a given session.
MS Paint: I don't bother with drawing anything now. I just assign a colour to each entity and move them with the flood tool (right-click = terrain colour). This lets me save a grid (with coordinates already added) to use as a template, or I lose that reuse a previous battle's grid with minimum fuss. Any further details go into a nearby Notepad window.
Skype: Used once, ever. I liked it, though, and it works well in place of a separate OOC chatroom. Awfully awkward when you come across some fantasy names, though... but frankly, that's a problem with the setting not the program.
physical objectsComputer: obvious enough.
Ashtray: for dice. Also a watch I'm not wearing that just happens to neatly corral the most frequently used dice together on the table next to me.
webMy own custom roller: In play, I prefer to use either the AIM thing so everyone can see the roll or use a physical die, so this is only to handle either many dice at once or hidden rolls for some weird non-Platonic, non-d10 die I don't have. Outside of play, I use it to get a "feel" for how often certain results should come up when testing a houserule or something.
Google/YouTube: Every so often I need a reference for something, whether because I want a specific effect or someone doesn't know what named object XYZ is. I can never prepare for exactly
what, though.
Bible Gateway: Because crazy religious references are always fun to throw in.
Behind The Name: I've found random generator results to be utter crap the vast majority of the time, so almost all my NPCs end up having "real-people" names which if I try to wing it all in my head often accidentally turn out to be "famous-real-people" names.
UglyNY.com: Recommended by a friend for reference pictures. Haven't really done much along those lines myself, but it could be useful when/if I run out of RL people I know to plug into my games as NPCs and I need inspiration.