Message board for finding private grants
In the US, students generally do not apply for grants (except for specific fellowships for graduate students - NSF, DoD, Hertz, and the like); it is the advisor's job to find funding for the student.

If you want to get a general sense of the funding picture in computational geometry, I suggest you look at recently funded proposals on nsf.gov (their abstracts should be publicly visible) and follow up directly (and with due preparation) with the principal investigator of the corresponding grant.

Your best bet is to attract the attention of a well-known researcher in the field, and, given the current academic pressures, they are very likely to have some funding for students.