This article is from the Credit cards and Consumer Credit FAQ, by firstname.lastname@example.org (Steve Adams) with numerous contributions by others.
Many cards assess an "over-limit fee" if you charge something that
takes you over your credit limit. They may or may not allow the
charge if they assess this fee. $5-$10 is common.
Some cards charge a late payment fee in addition to the finance
charges. Again, $5-$10 is common.
Some cards charge a transaction fee for cash advances. This may be
a flat amount (around $2), a percentage (1%-2% is common), or a
combination. These fees are in addition to the stated interest
rate, which usually starts accruing as soon as you get the money.
You have the right under the law to know what all these fees are
when you apply.