Well, it's now the week that ends with the first episode of Season Four, which means the TV guides are now out... therefore, look away now...
What's On TV (for example) has a roughly episode-by-episode listing, with one or two howling "plot is a secret" in one story but then "here's Johnny" in a side-bar!!
1 - modern London, Doctor is investigating alien activity (in London) where Donna looks him up and rejoins him; nemesis is Sarah Lancashire, a sinister business woman. Trailers on TV this morning seemed to show creatures growing off some random woman, a forming little gnomey things...
2 - Mount Vesuvius on the eve of its most famous event
3 - icy planet of the Ood
4/5 - UNIT vs Sontarans (includes Martha)
6 - "a secret" but includes Peter Davison's real-life daughter Georgia Moffett - for unexpected major spoilerage, see her Wiki page!!
7 - 30's England involving Agatha Christie (and Felicity Kendall as the Lady of the house)
8/9 - "scary" Steven Moffatt penned two-parter, featuring Alex Kingston
10 - set on an intergalactic spa under threat from aliens
11/12/13 - they've gone to the trouble of reporting that "details... being kept under wraps" yet at the same-time in a side-bar have a feature on Davros and "what will the mad scientist have in store for the Doctor in the dramatic series finale" - no clue there then!?
Wiki does also have an almost complete
episode list for season four