yoshi

Multifile Upload plugin adds some features to the WordPress’ default upload interface. You will be able to upload more than one file at a time. You can also resize the original image by specifying the size and change the thumbnail size when uploading.

Multifile Upload

This plugin allows WP's upload interface to handle multiple files at a time. User can also change the original and thumbnail image sizes.

huiz

The plugin affects the uploaded image while it is uploaded. Straight 
after it is uploaded, it it resized physically to the given width. 
There is no original image left, nor made a backup. Also EXIF infor- 
mation is lost.
A lot of WordPress users or developers who use WordPress as a CMS 
and want to configurate it for easy use, would like to have an option 
to resize uploaded images. Some images come straight from digital cameras 
and exceed 4000 pixels in width. So it would be nice to reduce that to 
the max width you use inside your WordPress theme.
If you want to keep control about perfect sharp and resized images, you 
better use photo editing tools on your computer, not a script like this.
The plugin uses a class originally from Jacob Wyke (www.redvodkajelly.com).

Resize at Upload

This plugin resizes uploaded images to a given width.

Multifile Upload vs Resize at Upload