A nice replacement for userreference widget would be welcome. Something along the lines of facebooks multiple user selector as in messaging and some other places. It would be perfect for user reference fields, privatemessages, user relationships, OG invites, rsvp and multitude of other existing modules. I think best way would be creating multiple (friends, fellow og members or any other kind of user) default user views that returns user picture and name (or any other field) and jquery magic on returned html and thats it...
I got very close to this by making view for use with userreference fields, got nice user list with checkbox besides each user, it was just too long list since there can be hundreds of users that view returns. I wanted them to be in div with overflow hidden and some search box/first letter selector to quickly find user as well as some tab or dropdown select to choose particular view that returns list (like friends or fellow og members).

Comments
Patch userreference?
Have you considered submitting this as a patch to userreference rather than (or at least before) creating a new module?
no, i was thinking of some
no, i was thinking of some sort of general module for many kinds of user selection tasks. that would be compatible with user reference and other modules could easily adopt it too.
As a CCK field module author,
As a CCK field module author, I'm with sreynen on this one - you'd be better off helping to either patch an alternative widget into the existing user reference module, or providing some settings for the presentation of the user reference widget (checkboxes and display code to show user pic, profile fields, etc - even leverage various profile extension modules) and supporting display formatters. This way:
If you are trying to avoid creating a content type just to contain a user list, then you might see if you can repurpose the Flag Friend module as it appears version 2.x supports arbitrary relationships for user lists, and it looks like it has a more FB-like user browser interface.
Doing
I'm about to do this on D7
Hopefully just a day's work. Here's what I've got so far
/*
* User choose module
*
* Just a special form field at the moment, no configuration pages
* Use it like this:
* $form['fieldname'] = array(
* '#title' => t('Blah blah'),
* '#type' => 'user_chooser', // or 'user_chooser_role' or 'user_chooser_permission'
* '#options' => 'callback_function' // or the role id or the permission key
* //etc.
* );
* where $callback is 'permission', 'role', or your own callback
* your own callback should return a list of usernames, with uid keys
*
* This module will modify $form_state[values][fieldname] to be the uid, regardless of what was selected
*/
I could use some help with the form element and the return values which I found rather tricky in Drupal 6
ok dunnit
http://drupal.org/project/user_chooser