Good survey of the multiword expression problem in NLP ?

I'm going to assume that you're interested in 'term extraction' or 'keyphrase extraction', which isn't exactly the same thing as multi-word expressions.

If you look at my blog post on KEA Keyphrase Extraction as an XML-RPC service, I link to existing code.

I also write:

There is a wide aca­d­e­mic lit­er­a­ture on term extrac­tion, which I won’t sum­ma­rize here. The best intro­duc­tory tech­niques are writ­ten by Park, who is now at IBM: “Auto­matic glos­sary extrac­tion: beyond ter­mi­nol­ogy iden­ti­fi­ca­tion” and “Glos­sary extrac­tion and uti­liza­tion in the infor­ma­tion search and deliv­ery sys­tem for IBM tech­ni­cal sup­port”. You can read more about how to roll your own ter­mex imple­men­ta­tion here.

I have a much longer list of references, but I suggest you start there. If you want me to post a longer bibliography, I can do so.

This is a little more specific, but when doing research on an idiom identification and extraction system I came across a very good reading list for MWE/idiom extraction papers here:

http://www.coli.uni-saarland.de/courses/cacl10/reading.html

Not a newer paper, but still with good results for verbal expressions:

Unsupervised learning of multi-word verbs Don Blaheta , Mark Johnson Proc. of the ACL/EACL 2001 Workshop on the Computational Extraction, Analysis and Exploitation of Collocations, 2001