I get my PS tips in the mail, almost daily. Don't know if they're usefull for anybody here, but I can post some.
1
Create high contrast grayscale imagery in Photoshop
Open an RGB image in Photoshop. Choose, Image > Adjust Channel
Mixer and in the resulting dialog box, select the Monochrome check
box. This will convert your image into gray values. Then adjust
the sliders for the Red, Green and Blue Source Channels back and
forth to boost the image's contrast
2 this one I really liked.
Resampling images easily in Photoshop 6
If you have to resample a series of images to match the size and
resolution of one image, you can do so in Photoshop 6 quickly and
easily. First open the image with all of the proper settings. Then,
open an image that needs to be resampled. Choose Image > Image Size.
In the resulting Image Size dialog box, select the name of the image
that you want to match from the Window menu (it will be one of the
last items listed in the menu). Then click OK in the Image Size dialog
box, and Photoshop automatically updates your image to match the specs
of the original image.