Ever heard of the gredic.com Word List? If not - you should have: it’s probably the most complete (6,500+ words, includes all of Barron’s and Princeton Review) and comprehensive word list out there.
Anyhow… now that same wordlist is available in a format for mobile devices: just point your cell phone browser to GREWL.mobi and boost your vocabulary! The pages are very lightweight, works like a charm!