In Claremont

Scripps College
Scripps Math Department
Claremont Colleges Mathematics REU Site
Claremont Center for the Mathematical Sciences (CCMS)
Claremont Colleges Mathematics Colloquium

Elsewhere

Mathematics Association of America (national)
MAA (SoCal-Nevada section)
American Math Society
Association for Women in Mathematics
Putnam Competition
Number Theory Web
Mathematics Genealogy Project