scribu

This plugin improves the gallery template by making the following tweaks:
<ol>
<li>Puts all the gallery css in a separte file, for easy customisation and faster page load.</li>
<li>Adds an id attribute to the code, so that two or more galleries can have a different number of columns and still display correctly on the same page.</li>
</ol>
Links: <a href="http://scribu.net/wordpress/improved-gallery" rel="nofollow ugc">Plugin News</a> | <a href="http://scribu.net" rel="nofollow ugc">Author’s Site</a>

Improved Gallery

Improves the built-in gallery in WordPress 2.5 and newer.

HETWORKS

You probably know that the speed of your website is important for both user experience and for your search engine ranking. The people 
at TinyPNG.com offered this great service where you could upload your PNG images and shortly also your JPG images, to have the file size 
shrinked to much lower amount of data, without a noticable reduce of image quality. And that is great! Compare your Google pagespeed score 
before and after you shrinked your images. You will gain many points.
The disadvantage of using TinyPNG is that you had to use the service upfront, before you could upload your images into your WordPress 
medialibrary you had to upload them to TinyPNG and download the shrinked files again. When the images were already in your medialibrary you 
had to do this all over, also for the images that were cropped by WordPress into the different filesizes. With this plugin that is all history. 
You just upload your images and as part of the proces these images are processed by TinyPNG.
This is what TinyPNG say themselves: 
How does it work? TinyPNG uses smart lossy compression techniques to reduce the file size of your PNG files. By selectively decreasing the 
number of colors in the image, fewer bytes are required to store the data. The effect is nearly invisible but it makes a very large 
difference in file size!

WordPress Image shrinker

Reduce image file sizes drastically and improve performance and Pagespeed score using the TinyPNG API within WordPress. Works for both PNGs and JPGs.

Improved Gallery vs WordPress Image shrinker