Involve (ISSN: 1944-4184)
“is a publication in between the extremes of purely undergraduate research journals, which in general are aimed at undergraduate audiences, and mainstream research journals.”
Math Horizons (1072-4117)
Published by Mathematical Association of America
Is a vibrant and accessible forum for practitioners, students, educators, and enthusiasts of mathematics, dedicated to exploring the folklore, characters, and current happenings in mathematical culture.
American Journal of Undergraduate Research (AJUR)
“A refereed journal for undergraduate research in the pure and applied sciences, mathematics, engineering, technology, and related area in education.”
“publishes articles from all branches of mathematics, as well as regular features on mathematics in the classroom, a computer column, letters, problems and solutions, book and software reviews.”
Plus is a free online mathematics magazine aimed at students of 15+ and the general public. "features math-related articles, puzzles, and ideas"
SIAM Undergraduate Research Online (SIURO) "is a web-based publication devoted to undergraduate research in applied and computational mathematics."