I'm trying to find out if anyone knows about an already existing jQuery plugin that will count up to a target number at a specified speed.

For example, take a look at Google's number of MB of free storage on the Gmail homepage, under the heading that reads "Lots of space". It has a starting number in a <span> tag, and slowly counts upward every second.

I'm looking for something similar, but I'd like to be able to specify:

• The start number
• The end number
• The amount of time it should take to get from start to end.
• A custom callback function that can execute when a counter is finished.