Well, I've got something you might like. It's just been released and I have 6 associations using it and several more evaluating it.
Its prototype has been in use for two years by the Portland Basketball Officials Association (~330 members and ~200 schools). It has been used for distributing assignments and accepting/declining assignments, member evaluations, registration, and more.
The assigning for the PBOA was done offline and imported. Now, it can be entered online in a manual fashion, with auto assigning features now in development.
Several of the assigning features are still in the works and should be done within a month or so. It will be able do auto assignments based on availability, scratch lists, qualifications and, eventually, geographic locations.
However, it is MUCH more than assigning software. Its a full communication and website package for sports officials associations of nearly any sport.
Go to
http://www.reftown.com
Drop me an email if you'd like to have access to the sample association to try it out.
See also a ppt presentation at
http://www.reftown.com/reftown.ppt
Lastly, if you have any suggestions or comments, feel free to let me know. There are new things being added nearly every day.