As I know,
a) CMU: Lots of applicants were rejected last week...maybe you are on the waitinglist...
Gatech: Someone has received the offer.(stipend $19500/year or something like that)
c) Caltech: There was an "interview and visit weekend" during Feb.23-Feb.24. Hope that the results would come out soon... (But I find that someone reported his offer on thegradcafe on Mar.20 last year ... Anyone hear any news from Caltech? )
(all of them for CS PhD)