I'm using an iPhone App called EasyBib and I'm really liking it. This app allows you to scan a bar code on a book using your iPhone. The bar code is then converted to a bibliographic citation!
You can choose from MLA, Chicago/Turabian or APA styles. After your citation is ready you simply email it to yourself.
I'm using EasyBib to quickly and easily format citations for the history and genealogy books I review here on Olive Tree Genealogy blog. Not only does it save me typing everything out, it ensures that I've cited the book correctly and in a consistent format.
A friend mentioned that she plans to use EasyBib to scan the books she writes and publishes. I am planning on spending a day scanning the genealogy and history books in my own personal library. Then I can email those citations to myself, and click on the Save To EasyBib link that is automatically inserted into the email. That link takes me to the EasyBib website where I can save all my citations in a list, then choose from several options for the list:
I can export my citations to WORD or Google Docs
I can copy and paste them
I can email them
I can also sort my list of citations alphabetically, by date, by tag (keywords which I add manually) or by source.
I am also able to print my list of citations, or save to GoogleDocs or Save for later on the website.
One caveat - many of the genealogy books that I've purchased for my personal reference library do not have bar codes. However I can manually enter the ISBN number and EasyBib searches for the book. If it is not found, I can enter the title, author and publisher plus date of publication on the EasyBib website and it is formatted for me correctly.
EasyBib is free from the App Store.