Displaying Percentages in a Progress Bar
David Stone over at Bare Naked App talks of using a background image to display percentages in a progress bar. The technique could also be used for bar charts or poll results.
What I've traditionally done for these kinds of things, since the image can stretch left to right with no degradation (in other words, there's no horizontal pattern, just a vertical one), I usually just use an image that is 1 pixel wide and set to a specific width based on a percentage of the available space. The width is calculated server-side (as is the background position in David's example).
To do the rounded corners, though, I'd need 3 images (background, progress bar, and overlay) so their approach does have its advantages (it only requires two images — progress bar and overlay).
To check out an example of what I mean, you can check out this site I worked on. (yeah, just ignore the layout tables.)