I remember back in the first Blues Brothers movie Dan Aykroyd said something like "In the future you will only be able to hear blues music by checking out records at your local public library." He was right--the public library is a good place to look for blues music. I finally went to my public library the other day, filled out the forms, and got my library card. Remember when you were a kid and that getting your first library card was a big thrill? I immediately wandered over to the cd racks and started browsing...... In about 5 minutes I was able to check out "New Orleans Piano" by Professor Longhair, (1972, Atlantic) a really good cd made up of sessions in 1949 and 1953; and Hubert Sumlin's cd "About Them Shoes" (2004, Tone Cool Records) an all-star set featuring Levon Helm on drums, Mudcat Ward on bass, James Cotton and Paul Oscher on harp and Eric Clapton, Keith Richards and Bob Margolin on guitar. l felt like I was stealing when I checked out those cds and walked to my car!
Two common sense reminders: First, you should always treat the cds you check out with proper care--the next person who wants to check out that cd is depending on it. Second, take only what you need and keep it only as long as you need. At my local public library you can check out 5 cds for 3 weeks, but my personal rule is to only take two at a time and take them back in just a few days.
I'd say that your local public library in one of the three foundations to your blues collection, along with the your local independent record shop (you do have one of these, right?) and borrowing music from your blues loving friends.
Keep the blues alive.