From Battlegrounds Games:
BRPG is a virtual tabletop program that provides you with all the tools you need to conduct a role-playing game session: a battlemap - with an optional hexgrid or square grid - on which to place and move your digital miniatures and props, a virtual dice roller with both standard and polyhedral dice, text chat functions, and a Fog-of-War feature that lets you gradually reveal the game map as the players explore.
BRPG can be played online with up to 15 players plus the Game Master. It can also be used offline in face-to-face game sessions (with a projector or HDTV), essentially serving as a digital battlemat.
Battlegrounds is easy to use, cross-platform (Mac OS X and Windows), and supports roleplaying in any genre and with any RPG rules system. Battlegrounds can also be used to play most boardgames and wargames.
Features a user interface that hides away when you don't need it, to avoid on-screen clutter and heighten the immersion factor
Photorealistic 2D dice and an incredibly-powerful dice roller that supports most RPG game die-rolling mechanics, yet requires absolutely no scripting
Built-in text chat with support for group or private chat, in-character and out-of-character chat, chat aliases, chat macros (for the GM's "read-aloud" text or for frequently-used dialogue), an exportable Chat Log, and more
A highly-configurable Turn Sequencer helps keep your game zipping along; it ensures that everyone always knows whose turn it is (or if their turn is coming up), and also keeps track of important character stats
The Fog of War feature uses either manual GM-controlled reveals and/or dynamic reveals (based on light sources present and each character's unique vision type)
Display visual aids and play music and/or sound effects
Support for card decks, including custom card deck creation
A token-swapping feature lets you easily switch token poses (standing, prone, mounted, etc), or "flip" virtual counters
Area of Effect overlays let you easily show what part of the map was affected by a spell, explosion, etc.
Pop-up character portraits, range measuring, a full assortment of drawing tools, and much more round out the feature set
"Out of the box" support for any RPG system; no need to purchase additional rulesets
More recent versions of the software are often available on the publisher's site, as beta releases.