On October 1, 100,000 lucky users got an invitation to preview Google’s new real-time communication platform: Google Wave. It combines email, instant messaging, chat, project management and social networking in a client that sits within the browser. To learn more, read Mashable’s guide or watch Google’s video .

“What are you doing?” Twitter is a micro-blogging social networking site that asks that one question, and gives you 140 characters to broadcast an answer to all your friends, family and co-workers. Intrigued by the possibilities? Here are a few guides to get you started: MasterNewMedia’s Twitter – A Beginner’s Guide , Caroline Middlebrook’s Big Juicy Twitter Guide, and Rafe Needlemen’s Newbie’s Guide to Twitter.

As spam instant messages (IM) become more and more prevalent, it’s a good practice to configure your IM software to only accept messages from people you know. In AIM, click on Edit, Settings, and then click on the Privacy settings, and then choose “Only Allow Users on my Buddy List.” For instructions on how to set this option on other popular IM clients, read Ask Leo.

POS means “parents over shoulder” but COS doesn’t mean “children over shoulder.” It means “change of subject.” To keep up with all the latest chat acronyms, try NetLingo, Big Blue Ball or AbbreviationZ.

As instant messaging has grown in popularity, it’s also fallen prey to the same marketers that made “spam” a household word. According to Ferris Research, spim (unsolicited commercial instant messages, also called “instant spam” or “IM marketing”) doubled last year. How can you stop it? AOL IM ( http://www.aim.com ) gives you the option of only receiving messages from known contacts. ICQ ( http://www.icq.com ) goes one step further, and lets you filter out offensive words and Web links.

To send a text message from your computer to a cell phone used to require that you knew the recipient’s cell phone provider and the exact syntax of their address, such as 1234567890@mobile.att.net. But with Telefilp you can reach almost all mobile phones with one easy to remember syntax: 1234567890@telefilp.com . The Telefilp service is free and does not require any setup or registration.

If you are a big instant message user, you probably have accounts with multiple vendors such as IRC, AIM, ICQ, MSN, and Yahoo! Messenger. But switching between so many applications can be cumbersome. Trellian gives Windows users access to all their instant message accounts from one application. There are free and fee versions to fit all pocketbooks.

Instant messaging (IM) is a more conversational medium than email because IM happens in real time, with all the participants online at the same time. When choosing an IM application, remember that all parties you want to message must be on the same platform. Here are the most popular IM applications: AOL Instant Messenger, Yahoo! Messenger, MSN Messenger and ICQ.