I've been doing some reading and research on Mandelstam, who I've come to rather late, and I came across this useful Indian blog with Mandelstam references. Looks like it may have other useful stuff.
The biggest problem for non-Russian speakers is to find a good translation of Mandelstam's poems. My main source at the moment is a borrowed copy (thanks Brian) of the Clarence Brown/W.S. Merwin Penguin translation from 30 years back. I'm aware of Brodsky's and Nabokov's criticisms of that version. I'm on the lookout for others.