DIY

With frugalism becoming fashionable, consider participating in the trend (as painful as it is) by making your own art. For $30 and the cost of a box of crayons, you can have 72 works by Richard Prince with his recently produced coloring book, 3rd Place. If you want a more diversified collection, you could get another coloring book, Between the Lines: A Coloring Book of Drawings by Contemporary Artists (2007). Between the Lines contains drawings by Julian Opie, Sol Lewitt, Vito Acconci, Rita Ackermann, John Baldessari, Jeremy Blake, Will Cotton, R. Crumb, Keith Haring, Robert Longo, John Lurie, Robert Mapplethorpe, Jason Middlebrook, Laura Owens, Alexis Rockman, Kenny Scharf, William Wegman and John Wesley, among others.
If you don't want to invest in crayons and are more interested in three-dimensional works, you should get The Paper Sculpture Book (2003). Originally a show at the Sculpture Center in NYC, this book is essentially the exhibit. 29 artists created sculptures that could be created from sheets of paper and provided detailed instructions on how to recreate them yourself. Sarah Sze, Fred Tomaselli, David Shrigley, and Glen Ligon are some of the artists. I received that book as a Christmas present in 2003 (thanks, S!) and love it.
All of these books are available on Amazon.