OAuth is hard. I don't care if you're the greatest engineer on Earth, at first glance OAuth is a WTF moment. Having a slew of Classic ASP sites to maintain, and no luck finding any help in the VBSCript OAuth department, I dove in to the HELL that is OAuth. When I'd finally emerged, although scarred for life, I had a full fledged OAuth implementation... done entirely in VBScript... OK, not entirely... but mostly no doubt.
Check it out here: Classic ASP VBScript OAuth