G-Portal UK Mobile Sites, http://cms.da.gp/

Great site that, once used, is almost impossible to forget, meaning that you've got access to it whenever you need it.

The URL that it's on is a real help, because it means that getting to the site from a mobile phone is really easy; no fiddling with long URLs.

All the links on the portal have been tested to work properly on a mobile phone, and all the sites offer genuinely useful or fun services.