Is There a Way to Share/swap Kindle Books with Other Kindle Users?

Yes, but not all books can be loaned. You can do it through the "Manage Your Kindle" link on amazon.com If it can be loaned, you'll see a special icon when you hold your mouse over it. The loans are just for two weeks and then the book will automatically disappear.

Many libraries also now have loaning programs, so you should look into that as well. Amazon prime members can also get some books for free.

Also, I just read Jo W.'s answer below and it is not correct. You do not need to give anyone your amazon password so they won't have access to your full account. You DO need to give the email address associated with your amazon account in order for them to send you the book.

Amazon has a lending program for Kindle users to loan to each other, however not all titles are available.

http://www.amazon.com/gp/help/customer/display.html?nodeI...

Also, if you are an Amazon Prime user ($79 per year), you can use their library service.

http://www.amazon.com/gp/feature.html/?docId=1000739811

Check to see if your local library has an e-book lending program. Ours does. You check out an e-bk for 2 or 3 weeks, and when your loan period is up, it just disappears from your e-reader. Kinda cool!

You can also check out lendle.com - it's a free subscription service where you list the books you have that you'd be willing to "lend" to someone else and depending how many books you list will determine how many books you will get to borrow in return - it's the same policy, you only get to read the book for 2 weeks (it runs off your amazon account to lend the books out b/c it verifies you actually have the books to lend out)...I've used this service and find it great b/c there are a ton of members so there are a ton of books to read :)
I guess you can also choose to pay a lifetime membership fee of $25 as well, but I'm not 100% certain what all that entails.

Check out the website ebookfling.com - it is an ebook lending site. for every book you loan out, you get a credit to use to borrow a book. The thing is, not all publishers allow their ebooks to be shared.

The only way you can lend books is to give someone your amazon ID. Of course that also means they guy buy stuff and charge it to whatever cards you have stored.

My daughter and my husband use my ID, that is the extent of people I trust.

I am glad I came back to check on this. Although the books I let my daughter read I am not able to lend anyway it is good to know some can. :)