Jellyroll,
give this a try
Access hidden Preview features through Automator | Preview | Mac OS X Tips
(there are a few other write ups on the web- just search for things like OSX, automator, re-size...)
You can of course use many applications to resize images one by one, but if you have more than one at a time to do- and you want to do them all to the same size (such as uploading whole albums to image hosting sites) this way can't be beat.
(this is what I use all the time)
Basically, you use a bundled application called 'automator' (depending on your operating system it should be in your applications folder)
it sets up a 'workflow' that automatically resizes as many images as you want- all at once, one after the other- and then saves them to a folder where ever you determine.
It takes just a little time to figure out- but is SO worth learning I cannot recomend it enough.
The way I do it, automator uses 'Preview' to resize the images- Automator can however set up workflows for many many different programs (to do many different things). It can also resize images through photoshop- but I have found 'preview' to work sufficiently for me.
I am not exactly a mac wiz, but let me know if you need any help.
I simply have an 'images' folder on my desktop, that I use as the
source folder, and also on my desktop a 'resized images' folder as the
destination. I dump in a heap of images to the source folder (from my camera or from Iphoto), resize them all effortlessly to the destination folder, bulk upload them all to my photobucket account, and then empty out both of the folders to the trash so it is ready for next time.
All up it takes a few minutes to resize 50+ images.
Hans.