Tooltips usually used to display extra information about an item. For example, you can use a tooltip to display description of a menu you hover in, show an image thumbnail, or maybe to display action list that you can perform for certain items.
In this post, I have collected 13 of them and hope that it will save your time in making your own. Some of them are free. But be sure you read the term first. And as always, if you got another good one, please leave in the comments.