Math Department Undergraduate Page: Some links and information maintained by the UCR Math Department (which overlaps somewhat with what's below here).
CNAS academic advising page for mathematics. This page contains links to some technical information on registration, advising, and transfer credit. It also has contact information for James Kelliher (the lead Faculty Advisor) and Michelle Butler (the Academic Advisor), both of whom can answer questions on the mathematics major/math program.
Course Catalog: This is the 2015-16 UCR Catalog, which includes descriptions of all courses as well as the requirements for the various mathematics majors. Mathematics is covered on pages 338-344 of the .pdf version of the catalog, which can be accessed directly at this link.
Tentative Course Offerings: This is a list of the undergraduate courses planned on being offered by the Math Department, as well as the term (or terms) when you can take each of them. In most cases the courses and terms remain the same from year to year. This can be useful when planning out what courses you need to take by when to finish your degree on time. For example, a BS in Pure Math needs 151a (fall only), which needs 145a (winter only), which needs 144 (fall and spring). So to take 151a in your senior year you should be taking 144 by the fall of your junior year.
UCR Math Undergrad Research This page has descriptions of some of the current and previous projects done by undergraduate mathematics majors working with graduate students as part of our research mentoring program.
Math Alliance: This is a national program designed with an aim of increasing the participation of underrepresented groups in the mathematical sciences, at the graduate level and beyond. In support of that goal, the alliance is developing a network of mentorship and support for students who are interested in possibly applying to graduate school. UCR has many mentors committed to participating in this; if you're interested in the alliance, you should contact one of them.