The Darling model kits (make sure to buy the inorganic/organometallic expander pack [http://www.darlingmodels.com/Individual-Orders-Molecular-Model-Kits/KIT…] along with the regular organic one) are the best I've found for inorganic.  They are big though, which is good and bad.

I agree with Adam.  Those are the ones my class uses!

I'm a big fan of the Prentice Hall Model Kits for General and Organic Chemistry (ISBN 978-0139554445). They're pricey, but can be bought used for less. In general they get positive reviews from our students.

Our organic students generally buy the Prentice Hall Organic Model kits.  What I've done for inorganic is to buy parts for students who want an inorganic model set.  So, for example, I buy bags of just the octrahedrals, and for $1, students can get 2 octrahedrals that work with the organic model kits they've already bought.  It's worked pretty well for my inorganic students.  We tried using this part approach to put together small, inexpensive ($8) model kits for general chemistry.  Some instructors have found this helpful.