I just finished working on the latest version of my Local Chat Gadget for Google Personalized Homepage and Google Desktop Sidebar. You can use the gadget on either of the two products to communicate with people in the same area as you.
By specifying your zip/postal code (or one near you), you will be connected with people in your area. To make sure the nickname you choose is never used by anyone else, provide any password in the optional password textbox (this effectively creates a new account).
Give this gadget a try by clicking the "Add" button at the top of your sidebar, then search for the following:
If you have any suggestions or comments about this gadget, feel free to leave them in the associated Google group here.