The Failure of Liberal Bioethics - NYTimes.com - on IVF and other related technologies
Gay marriage:
The slippery slope of gay marriage has begun - On Utah's anti-polygamy law being struck down due to gay marriage being legal (and more of gay marriage's own slippery slope)
The Volokh Conspiracy - The Slippery Slope to Same-Sex Marriage - On gay marriage and past claims that there would be no slippery slope towards it
Addendum: Gay marriage and the immediate pivot to trans 'rights' are another example of the 'myth' of the slippery slope (Google isn't indexing that page for some reason)
Euthanasia:
Legalizing euthanasia or assisted suicide: the illusion of safeguards and controls
Euthanasia and the Slippery Slope (links)