Check out kindleboards website for lots of great tips
The book bazar section as a thread specifically for free / cheap Kindle books.
Some are free for months, some weeks, some days, and some hours
I picked up 9 of the Lemony Snickets books during a mis-pricing once that only last about 6 hours. 
'Like' Inkmesh on facebook. They put up freebies as they find them, although they also do the nook & Sony readers.
They just released the Kindle 3, and at reasonable prices so you may want that one.I would love to get a Kindle II with the wifi, 3g. Could someone tell me about it and what the 3g is for? I know what the wifi does. I love to read but I dont want to drag books around. Do your arms get tired from holding it? Thanks Jo
I would love to get a Kindle II with the wifi, 3g. Could someone tell me about it and what the 3g is for? I know what the wifi does. I love to read but I dont want to drag books around. Do your arms get tired from holding it? Thanks Jo

(There's no monthly fee). I use that 3G for book buying, checking my email from time to time, and other mundane stuff
Just nice to know I have it.