CPG and
RedBook is available on iBooks cool thing about the CPG is that its in a different form than traditional iBooks (maybe pdf?) but you can "zoom in" on the different pages which works great considering the topic. There's also a couple apps I use to quickly determine varieties, but they aren't at all a "complete" resource. Pocket prospector, iCoins, and coinbook pro. All have a little something to offer.... I wish CopperCoins.com would make an app.
I find the Mint and Proof set guide in the
RedBook to be quite handy when CherryPicking the different sets on what to look for. Also the
ebay app to see what people are paying for what. Not that I want to sell anything off (other than to upgrade my collection), but it helps to know real world value in case I desperately need the cash.
Almost forgot "A Guide Book of Lincoln Cents" by Q. David Bowers - the best read for cherrypicking everything and anything
Lincoln Cent series - even has what to look out for from year to year and how to spot dipped coins and perfect strikes per year.