A few caveats:
- Some have dates which suggest they have expired. However, a company which offered an internship last year is likely to be offering one this year.
- Some may have a location or a specific preference for students from a specific school. Read the fine print.
- You can find many more than I've shown below--these are the first handful of resources that popped up. The best hunting grounds are going to be at schools with larger English departments, and thus targeted postings for that group.
http://www.stanford.edu/group/cellardoor/cgi-bin/home/2010/01/internship-opportunities-for-english-majors/ (Stanford University
http://www.english.lsu.edu/UndergraduateProgram/Internships/item38219.pdf (Louisiana State University)
http://english.barnard.edu/opportunities/jobs_internships#english (Barnard College)