It's important to remind ourselves: he's in judicial custody under on false charges.
There's now a website set up by his colleagues and students: Justice for Dr. Partho Sarothi Ray. [Update: A blog has also been set up on WordPress.com. This one is better because it allows readers to leave their comments -- see #4 below.]
The news of Prof. Ray's arrest and illegal detention has been picked up by Nature. Its India portal has a post by Subhra Priyadarshini, and its Nature News Blog has a post by K.S. Jayaraman, Nature's India correspondent.
Quite a few media outlets have covered this travesty. Justice for Partho site has a compilation of links.
A letter has been sent to Prime Minister Manmohan Singh -- after describing the case of Prof. Ray (and that of another professor from Jadavpur University, Prof. Ambikesh Mahapatra), it urges Prime Minister Singh to "personally intervene to resolve these matters urgently." You can read the text of this letter, along with a first list of signatories here.
Update: The letter has also been posted at at the Petition Partho blog. Leave a comment there if you agree with the contents of the letter.