Reload and go!
Amazon Gift Card Balance Reload makes it very easy to reload and go.  I buy a ton of ebooks and this is an easy way to keep track of my spending and there aren't all the small debits of $0.99 here, $7.99 here, and $4.99 here on my credit card.  Just one amount and when it gets down to less than $10, I simply reload again.
Rating: 5 stars