The following are web sites that deal with Micropatrology in general. Some are explanations of the phenomenon of Micronations, some are encyclopedic descriptions of Micronational efforts over the years.
l'Institut Franšais de Micropatrologie: As the name implies, a French-based Micropatrology institute. And yes, the site is in French.
Footnotes to History: Contains a lot of information on nations that aren't around any more, as well as several micronations.
MicroLINKS: Another "links to micronations" page, broken down by type of page (news, culture, politics, etc.).
The Micronations Page: A terrific listing of Micronations old and new, with lengthy descriptions of many of them. Has quite a discriminating criteria for entry.
The Microstate Network: A management consulting company that not only serves the smaller recognized nations of the world, but has information on "Model and Imaginary States" as well.
MicroWorld: A wealth of information about Micronations, including a newsletter "MicroWorld Monthly". They're currently putting together a MicroWorld Fair so prospective citizens can see different Micronations side-by-side.
While email is fine for person-to-person communications, some Micronations and individuals like to use the Usenet to broadcast their announcements and opinions to all and sundry.
These are somewhat different from the Micropatrological web sites, as these are UN-type groups and other alliances run by Micronations for Micronations (as opposed to merely being about Micronations in general).
Grand Alliance: Set up to resolve disputes among the member-nations.
League of Monarchist States: An organization designed to "perform a higher interaction" between those Micronations with monarchical forms of government.
Splendid Micro-Union of Microstatia: A relatively new, but apparently well-populated and active organization.
Union of Soviet Socialist Republics: A reformation of the historical USSR, this time in Micronational terms. I'm not sure how serious they are; Laputa seems to be the only member, and the title line of the web site is "The Evil Empire." Still, if they can pull it off, I don't see any reason why there shouldn't be a Communist intermicronational organization.
United Association of Micronations: At the moment, a project in development, being formed to make up for the inactivity of the LOSS and UM. Recent reports put it in the "inactive" category as well.
United Micronations: Seems to have curtailed much of its operations in recent days.