Most Gmail users are familiar with Google Labs, a nifty set of experimental features which aren't quite ready to be rolled out to all users, but are good enough for a select subset of users who like to try out new things.
According to Cnet's Natali DelConte, Twitter is planning a similar feature for the near future. At the FOWA conference in London, Twitter's user experience and front end engineering lead Britt Selvitelle said that it's coming "soon". The idea behind it seems to be a bit different from Google Labs; while Google is using it to test their own ideas, Twitter will let developers create add-ons for the site.