.PDF files are a fantastic vehicle for distributing information. They are only now coming into widespread use outside the commercial community, but are hidden amongst the world's cyber-clutter. As one comes to my attention, it will be included in this list. Please bear in mind that these often come and go quickly; and may not be available in the future.

Smithsonian Contributions to Paleobiology
The USNM now has many of their publications online as .PDF downloads, including the Lee Creek volumes.
Mesozoic sharks of southern England
Charlie Underwood
The Birkbeck website is hosting downloadable pdfs of most of Charlie's papers. These are largely associated with Mesozoic sharks of southern England
A comparison of isolated teeth of the early Eocene Striatolamia macrota (Chondrichthyes, Lamniformes), with those of a Recent sand shark, Carcharias taurus.
Steve Cunningham
Tertiary Research 20(1-4) pp17-31.
Pollack Farm Fossil Site
Delaware Geological Society
This is an original publication being released in .PDF format. It is well worth the download (3.2 MB). Bob Purdy wrote the paper on the Miocene shark teeth.