It's
www.balpa.org.
BA are the obvious ones missing from the above lists. They are not currently recruiting, and are unlikely to do so for some time, but they were the largest player in the sponsored cadet game for many years.
Most of the charter airlines have run sponsorships at various times, and many will again. Even Virgin Atlantic ran a brief sponsorship scheme in 99/00, when Virgin Sun needed low-houred pilots. Air Atlantique still run their apprentice-type sponsorship (the 'fugly' scheme).