The URL shortening service tr.im has shut down URL shortening via the web and announced that their API will be shut off by the end of the year. You can read the full announcement on their site http://tr.im/
I a few applications that use the tr.im API and I have noticed that the API calls now generate links using the is.gd domain name. It appears that tr.im may be taken over by is.gd although I have not seen any official announcement of this change on either site.
All users using tr.im will have to switch to another URL shortening service.
Currently creating a link with tr.im's API service will generate a shortened URL with the is.gd service instead of the tr.im service. I'm guessing this will continue until the end of the year. However, it is uncertain what will happen after that.