An interesting article on reducing bandwidth use, increase speed and serving you website visitors better
Images make up the majority of the Internet, yet we consistently fail to apply the most basic of optimizations. Even big sites like Twitter are completely screwing this up. Furthermore, there are huge unexplored areas when it comes to image optimization which would provide significant savings. We should stop worrying about esoteric performance optimizations when there is so much other low hanging fruit.
Full article: Overlooked Optimizations: Images / Stoyans phpied.com.