Jon has picked up on my quote blogmarklet idea and extended it so that it preserves the links and other source information in the quoted matter. That was on my list of things to do.
Links are powerful tools that we're still learning to use, but citation is a more than just linking. I'm becoming deeply interested in how we can publish fragments that are easy to cite and that, when cited, carry rich context with them. Phil Windley's quote bookmarklet is an example of what can be done. If you are running Mozilla and want to see a markup-preserving variation on that theme, select some text on this page and then click here. For best effect, sweep out a selection that crosses an element boundary, for example everything from "Windley's" through to "an example" in the sentence before the previous one. You should get this complete paragraph, a la Mozilla's right-click View Selection Source feature, plus some metadata.
Jon's entire post is worth reading as he gets into the issue of citations and URLs.