Positivity Learning Library:  
Use Power Clip in Corel Power Clip allows you to fill a shape with an image
Convert a jpeg to Vectorise in Corel Vectors give nice sharp lines, jpegs can look ragged.
Calculate Optimum Exposure Time How do you know that you are exposing your screens for the correct time.
Use Ghostscript and GhostView Free Postscript software - for geeks only.
Avoid Losing Details During Exposure Why you can lose elements on your positive during exposure
Separate Artwork to a PDF in Illustrator PDF is Postscript and a PDF printer can be used to separate artwork.
Understand How an ICC Profile Works ICC profiles explained
Anti-aliasing when screenprinting Why you shouldn't use anti-aliasing when designing
Trapping Making life easier for screenprinters