Tests on the comparative strengths of ice screws and ice threads from Petzl
http://video.google.com/videoplay?docid=1863958284744514965
The following links are to Kolin Powicks gear testing page on the Black Diamond site.
Retiring Old Ropes - How strong is an old rope
Is my rope still ok to use of I accidentally peed on it?
Connecting two slings together
The strength of climbing harness belay loops
Spectra vs. Nylon–Real World Wear
There are more links on a similar theme from each of the pages above.