I share an office with Hrvoje Benko and Gábor Blaskó at:

603 Schapiro, Center for Engineering and Physical Science Research (CEPSR)
Phone: +1 212 939 7077

I can receive mail at Columbia as follows:
 
Drexel Hallaway
Columbia University, Dept. of Computer Science
450 Computer Science Building
1214 Amsterdam Avenue, Mail Code 0401
New York, NY 10027-7003

Office:    +1 212 939 7077
Lab:        +1 212 939 7101
Fax:        +1 775 305 3477
E-mail:    drexel@cs.columbia.edu