It's easy - just select the desired access level, copy this link and send it via email, instant message, etc.Link: Just a link to your wiki. Post this anywhere and people can ask you for the invite key.
API Feature Requests
Visual data interface and widgets similar to those available at labs.digg.com. - Jon Gos
Support for Timezones in a profile - Offbeatmammal
Ability to search/filter on content and date range for posts from a user (ideally this would increase the max 100 limit, but be restricted in how often it could be run) - Offbeatmammal
Relationship API calls. eg. The ability to approve & request pending friend requests, etc.