The Once and Future Companion
Freema Agyeman has wrapped up her shooting for Torchwood (and her glamor shot for Marie Claire magazine) and is slated to begin filming her return to Doctor Who on Wednesday, October 24. She will appear in 5 episodes of the 13-episode season, and is the companion in the tie-in novels that have been announced.
Another familiar face returning to Doctor Who is Peter Davison. The BBC has officially confirmed the rumors that there would be a "Five and Dime" Doctor reunion, with the Fifth Doctor and Tenth Doctor both appearing in the Children in Need special.
Other familiar faces may be making a reappearance in their shows as well. Lis Sladen has said that the writers are at work on the second season of The Sarah Jane Adventures, although nothing has been officially announced regarding more episodes.