Here is a sampler of instant-messaging (IM) products. Currently, most popular free programs are incompatible with each other, so people using one program can communicate only with other people using the same program. (Think of it this way: it's like having Verizon cell-phone service and being unable to call anybody who subscribes to Sprint PCS or VoiceStream.)
While the IM industry struggles to find a common standard, many users of free IM programs simply agree to all use one service -- or bite the bullet and use several programs to make sure everyone's in touch.
The four most-used free programs are:
AOL Instant Messenger (www.aim.com): This popular, user-friendly program works on multiple platforms and doesn't require an AOL Internet account.
ICQ (www.icq.com): The original consumer IM program, it's powerful but less user-friendly to newcomers.
MSN Messenger (http://messenger.msn.com): This program sports an attractive, easy-to-use interface, and it's accessible from other Web-enabled computers -- but it was criticized last spring for security flaws.
Yahoo Messenger (http://messenger.yahoo.com): Another popular program, this one offers video chat and nice background "environments." It works with other Yahoo offerings.
Other free programs include:
Eyeball Chat (www.eyeball.com): This cross-compatible program allows users to send real-time or recorded video.
Jabber (www.jabber.com): This program is free for up to 100 users; fees apply to license additional users and for technical support. Jabber works on multiple platforms but is compatible only with itself.
Trillian (www.trillian.cc): This program's popularity has been skyrocketing because it's compatible with all other free IM clients, although users report continuing difficult in communicating with people on AOL Instant Messenger.
Here is a sampling of commercial-grade products:
All Instant: www.allinstant.com/home.html
Comverse (recently acquired Odigo): www.comverse.com
FaceTime Communications: www.facetime.com
IBM Lotus Sametime: www.lotus.com/home.nsf/welcome/sametime
Sprint (for wireless access to IM): www.sprint.com