Notice a bug in the Google web search results? If so, Matt Cutts wants you to report them to him on his blog. There is one big rule, Matt said:

I only want to see specific queries that seem to show bugs, and the more concisely you can explain something, the better. I’ll probably keep just the first example of what looks like a bug. I’ve got a meeting at noon tomorrow to talk about search bugs, so I’ll probably lock the comments after that.

So go ahead and report them.

Postscript From Danny: FYI, there's a dedicated area within Google for reporting bugs of all types, including web search bugs, and that area is regularly monitored. You'll find it here.