Wonderm00n

The WordPress default galleries always link to the full image size which can be pretty annyoing because most users upload huge pictures.
With this plugin you can set a default size for the galleries to link to. This can be thumbnail, medium, large or full.
For now this a global setting for all galleries, but on a future version I plan to let you choose a specific size for each gallery you create on your WordPress posts or pages.
It’s also possible to add arguments to the link (A) tag. This may be useful to add lightbox/fancybox script compatibility.
Based on the oikos.org.uk solution that can be found at http://oikos.org.uk/2011/09/tech-notes-using-resized-images-in-wordpress-galleries-and-lightboxes/

Wonderm00n's Gallery Link Size Changer

This plugin allows to change the way the Wordpress gallery links. You can select to…

Jose Conti

With this plugin you can add tools for Media
<ul>
<li>Add columns in Media Library: The new columns are File Size and MIME Type. The File Size column is sortable so you can find the files with the bigger size in an easy way.</li>
<li>Add featured image to post list and allow to add and change the featured image from post, custom post and page list.</li>
<li>Add the ability of customize every image link of a Image Gallery.</li>
</ul>
More features to come.

Media Files Tools

Very usefull to search and optimize large files

Wonderm00n's Gallery Link Size Changer vs Media Files Tools