It would make sense that Shelfari had a way to show that a book has been borrowed or loaned. And in fact there is a way to do this, and it's amazingly awful. Here are the steps:
1) Move the mouse cursor over a book in your shelfari shelf and click the green edit button.
2) Click on the "My Edition" tab once the edit window pops up.
3) Fill out the "loaned to", "loan date", and "due date" information in the window.
4a) If you want your children to check out books then to find out what they've checked out, simply follow steps 1 and 2 for every book in your Shelfari shelf.
4b) If you've decided to check-out the books for the children on a daily basis and don't have a photographic memory, follow steps 1 and 2 for every book in your Shelfari shelf.
With Friends Like These...
Next, my Google Search led me to...
Delicious Library 2 looks like Shelfari, and is made exclusively for the mac. It uses the built in webcam to scan bar codes, and the titles instantly pop up. This was better than Shelfari because you don't have to type anything.
But there are a few problems. First there is no mobile app for Delicious Library 2, and it doesn't look like there will be one any time soon.
Second, since Delicious Library 2 is not an online application, any online presence needs to be exported. Here are your choices: MobileMe, or an FTP site. That's it. This along with no mobile support is a killer for me.
It is easy to show checked-out books though:
Do you see that faded book in the left corner? That's a book that's been checked-out. I simply drag and dropped the book into my friends list on the left. The problem with this is you don't know when it was checked out. Only that it is checked out. So I was off to find another app.
Since Delicious Library 2 didn't have any mobile app version of itself, I decided to check the iPad app store. I found these:
Book Crawler isn't bad. But I am frustrated with the "list" view of the books that are inventoried. As with all three of these iPad apps, Book Crawler allows you to scan bar codes of books to enter them into the database. Book Crawler does have a "cover flow" view, but it is so tiny, and so difficult to navigate that it makes it worthless. The edit box of each book has a field called "loan" where you can type any name into, and then you can sort books by that field, but that's not very helpful to me.
iBookshelf was the next iPad app that I tried. It was essentially the same, but I couldn't find any way to show that a book had been borrowed. Next...
Book Keeper looks a lot like Delicious Library 2 and Shelfari, except that the graphics for its book covers use the lowest resolution humanly possible. There's an example below, but once again I didn't like how limiting it was to check-out a book. There is a "loan to..." field in the edit box, and that's it.
Here's how the cover should look of When Charlie McButton Lost Power:
And here is what it looks like in Book Keeper:
I gave up on iPad apps and went searching online again. I finally ran across this free service:
Classroom Organizer is entirely online, and there is a mobile app for it as well. The mobile app's function is to use the iPhone or iPad camera to scan books into the online database. It's incredibly convenient. Each student can also be entered into the database, and there are loads of check-out parameters that you can control, such as how long a book is allowed to be checked out, its condition, or if an overdue notice should be emailed to the teacher automatically. Reports can be easily generated in a variety of formats as well.
It's not a perfect app. It doesn't recognize some books that it should, and I can't import cover art if it doesn't recognize a book. But it's very good, and what I'll be using this year.