Have been using Yahoo Groups on and off for a few years. In fact, I started when they were eGroups. More recently I have been active in one of our alumni groups. Here is a wishlist based on the things we want to do.
1. A better database facility. It will be nice to have types associated with the columns in a table (like date, number etc). This will not only allow us to create better tables but create nice views by sorting them on various fields.
2. A facility to make all the objects url addressable. To a limited extent it is already there. But would love to have it go granular.
3. A capability for transclusions. It should be possible to mark a paragraph in a message or a file, get a url to address the paragraph and include it another message. When users view the message, the original marked text can be extracted and made part of the message.
4. Ability to create blogs by individual members.
5. Improved Calendar capability – Mark a range of dates and associate it with an event (like a get together).
6.Integrated HTML editor (like the ones available in a blog) so that people can put up better looking posts including pictures.
7. An API for yahoo groups would be great.
8. A portlet interface would be cool. So I can bring in stuff from outside and integrate it into my group.
9. Capability to tag posts. Something like what furl or del.icio.us does. It will be easy to locate posts and moderators can also tag them.
I think I will pause here. Even though I have a lot more, if I get some of these, I will be happy to do a lot of things with the groups.
It is cool that Yahoo Groups allows the capability to generate RSS feeds.