I've done some nice book and video sales on Amazon.
Copywriting books did well for me. I found some at "Half Price Books" stores. As an example a George Haylings book I sold for $100, a Eugene Schwartz for near that.
Also, some NLP books are good.Another are DVDs of Russian Systema Martial Arts by Vladimir Vasiliev. Scott Sonnon DVDs do well also.Another are Carlos Castenada DVDs called "Tensegrity". The best was the Systema. I got many requests from Amazon asking if I had more copies. I could have sold 20+
Look at some of the online rare book stores to get an idea on pricing.
I've lots of high cost marketing/copywriting courses too but, they were not in Amazon's data base.
Craigslist has worked well for some hardgoods in the past.
Things from alternative medicine did well like water ozonators,filters,air purifiers.
with job loses and high gas prices you might do well on Amazon with stuff related to Bicycles. LOTS of traffic on that also, kits to make your bicycle electric with hub motors from ...you guessed it China

I gave up though selling stuff under $20 as the time to pack it up, print labels, take it to the UPS or USPS is worth something.
Some are making a killing shipping cds and dvds as the packing is tiny, costs pennies and shipping cost is low.
I'm looking to do some Kindle Books if anyone had tips for that it would be great.
With the release of Amazon's $139 new Kindle I suspect that is going to be IN-FN-SANE for the Holiday selling season.
Off topic, rumour has it iPhone might be going to allow T-Mobile! AT&T is soooooo much crap if Apple would just get a decent service Jobs would be Sainted, Made King and Obama would probably want to have his baby
