Is there a cherrypicker guide or other resource for what block numbers and whatnot are worth more than face? Maybe my googling skills are really that bad but I couldn't really find anything online.
A popular site for currency collectors is Track & Price (annual fee), http://trackandprice.com/u-s-currency-online/ You can access some auction sites that are fee-free and then research recent auction results, the two I use the most is Heritage and eBay. https://www.google.com/#q=online+paper+currency+auctions+
I remember a member mentioning a bill that had some serial or block position that was valuable for some reason. Or maybe I'm just too tired right now
I have wondered the same at times. I have seen many listings for bills that claim the note is from a rare block. How do they, or I for that matter, know this is true. I know of no documentation of specific block numbers except more recent issues.
I'm always paranoid now that I'm spending some super rare note or whatever. Probably shouldn't hold my breath too much though...
Standard Guide to Small-Size U.S. Paper Money 10th edition. John Schwartz and Scott Lindquist. It'll give you prices on certain blocks. For instance, it lists the 1928G $2 Legal Tender D-A block as $75 in CU and the E-A block in CU at $50. At the time of printing (2011) if the series didn't have any "scarcer" blocks they would simply give you a range of blocks known for the series. It's a great book and I recommend it to anyone interested in paper money.