The Floranta AJAX libraries are used to build Rich Client Wikis. Editable sticky notes can be created and positioned over any Web page (even plain HTML), and are capable of behaving as if they stored their entire state in the page. Floranta enables collaborative teamwork and creative activities like cartooning and collage creation, personal notes, ToDo lists, and blogging.
Fruit Show is a minimalist forum package based on the forums at joelonsoftware.com. It is based on the philosophy that social atmosphere is a by-product of software design. There's no registration and very few features for visitors. It's skinnable and easy to install. It also contains some unique moderation features. Fruit Show is intended for small sites that need an easy to use and accessible forum.
Pipo-BBS allows you to install a BBS server and clients. You can chat via a nice interface with an unlimited number of people (as with IRC). This software is in a pre-release state; it is still very alpha, and can be difficult to even compile. It works under linux, MkLinux, SGI, HP-UX, and Solaris. The only interface for this BBS is telnet for the moment; an interface using GTK has been started. It has been translated into French, English, Spanish and German.
Globe*Trotter is a guestmap. It allows Web site visitors to mark where they live on a map and include their personal comments, instead of merely tacking their personal regards onto the end of a long list. It benefits your visitors because they can easily read other's comments and add their remarks in a fun and novel way. It also benefits you, the webmaster, because more people will be likely to give you feedback and you will be able to see where your visitors are. A free hosted version of Globe*Trotter (with no ads) is available.