You need to use a Jabber (aka XMPP) client. It works from Google Mail and Talk.
Factbot is pretty basic just now and it may improve.
In case you don't know... "bot" is short for "robot". It's program that acts like a person. More info on bots in general.
2010Feb13: Server has starting sending pings so we now reply with a pong.
2010Jan27: It now puts a new random fact in its presence every ten minutes ;)
2010Jan26: Switched from SSL on port 5223 to STARTTLS on port 5222.
2010Jan21: Made some nice improvements in the way it stays reliable. Before it would detect if it wasn't communicating with the server and restart. But that always seemed a bit crude. So now it automatically updates its presence every 10 minutes. This seems to keep the server much happier resulting in far fewer forced restarts. A neat side-effect: it puts the date/time in its presence now and you can see that.
2007Apr4: Added the whyis command! Now you can see what facts support its reasoning. Try: whyis Pluto bigger than sun
2007Mar31: Fixed a another reliably problem. Seems it was unable to restart its self when it sensed a bad situation. Now it can.
2006Sep27: Today we fixed a bug that stopped the bot from being robust during server or Internet outages. So it will now be up a much larger percent of time.