There is an excellent article by Jeremy Pierce (a.k.a. Parable Man) refuting the famous "Shell Fish" argument - an argument which President Obama has notably repeated in defense of his pro-homosexuality policies (which just goes to show that a law degree from Harvard doesn't necessarily preserve one from presenting obviously fallacious arguments against clear Scriptural teachings).
If you've ever read the Pentateuch and wondered why homosexuality is still wrong, but eating shell fish is now okay - yet both are called an abomination in the Old Testament - you'll want to check out Jeremy's short but sweet article. He adds the missing element to the discussion: viewing the shell fish issue in its original historical context rather than from our 21st century cultural point-of-view. I added a little note in the comments.