If the text above them is green, it indicates that the presenter is somewhere in Second Life. The visitor can then just click on the bell to summon the presenter with a quick message.
If the text is red, the presenter is not in world. However, a message can still be sent and it will show up the next time they log in.
Now this can be problematic for users who created a Second Life account exclusively for the purpose of presenting or attending a SciFoo Lives On session since they are unlikely to login again and retrieve IM messages. There is a trick around that: in SL hit control-P and turn on the setting to forward IM to email.
This effectively transforms the SciFoo Lives On area into a perpetual session with the cumulative content of all prior sessions, which now include "Tools for Open Science" and "Medicine and Web 2.0". We are now getting ready for the "Definitions in Open Science" session on Tuesday Sept 4, 2007 at 16:00 GMT and there are still slots available to present.
The bells can be purchased for 150L (about 60 cents) on PixelTrix Island (SLURL) - thanks to Ron Comer for help in locating these!
The location and list of all upcoming SciFoo Lives On sessions can be found on the SFLO wiki.
