GeoURL tags and HelloWorld maps attempt to recreate the idea of community based on physical locality, but don't help to unite dispersed individuals based on shared ideology. Here's an idea for enhancing personal communication in future ubiquitous networks, that could also work quite well with the systems we already have in place. I'm sending this to the LazyWeb in case anyone else can sort out the practicalities.
Tentatively titled ChatNap, this could feasibly be an IM plugin. I've noticed people changing their screen name to reflect their mood, and thought why not make this a built-in feature of the messaging system? At the start of the day you can enter keywords that describe what's on your mind or what you want to talk about that day. This is sent to a central server, be it Jabber, Slavanap, IRC or whatever. You can then either actively search for people who share your interests, or you can sit back and wait for anyone interested to get in touch. This is real P2P - sharing ideas rather than files. If you're an expert you can offer your advice or look for collaborators. If you're fed up with Google you can ask someone else for hints, or take part in collaborative searching and browsing.
It's possible to envisage this system extended to other communication devices, while subcategories could enable other uses, such as finding people in your geographical area, matching physical characteristics or advertising items wanted/for sale.
Practicalities
At the moment, running a Jabber Perl script would allow users to send their keywords as an instant message to this central Jabber client, which stores them in a database. If 'find' is added to the start of the message, the Jabber client will search the database and return a list of users with matching keywords, which the user can then contact in the usual way.
Problems and workarounds
Privacy: By using a separate username for this service, a user can just dump that name at any time, and their everyday identity is never disclosed. Alternatively, route all conversations through a central server so that user's identities are kept private.
Spam and noise: By building more precise keywords (eg information AND visualisation NOT cinema), the area of interest can be increasingly defined (at the cost of less exposure). A rating system could also be employed: after each conversation you rate your correspondent, and can elect to only receive messages from users rated above a certain level.
Lack of users: Make this as simple as possible to use - eventually automate the process within IM clients.