Today is Red Nose Day in the UK, some sort of charity thing like Comic Relief. It is an all day telethon. It will include a Sarah Jane skit (probably about 15 minutes). Might get included on a future dvd release.
For Red Nose Day 1999 there was Dr. Who skit that had Hugh Grant, Rowan Atkinson, Richard E. Grant, Jim Broadbent, and Joanna Lumley as the Doctor (he kept dying and regenerating). It was quite amusing.
As part of RDN Google created drwhoogle.com. Proceeds from it will go to charity. Other than the name though, I haven't noticed anything special about it from the few searches I did.