What do you have? What kind of job is it for?

Send something that got published and garnered commentary in the press. The green nabobs always rate job performance in either column inches or contributions raised. They don't really much care if you accomplish anything, just so the grant funders notice them and/or money rolls in.

I've got nothing published. I have 5+ collective years of writing on my weblog and my community weblog.

This place cares about results more than $$. They've been very successful getting industrial companies to clean up their acts.

Should I state the obvious? Pick a post that has to do with environmental issues?

Two! You go, boy.

In that light, sciurus, I'd definitely pick something that is both issue-oriented and showcases your persuasive writing ability. Something in which you build a clear, strong, and forceful argument, rallies the reader, and shows good writing style at the same time.

Excerpt it from your blog and lay it out nicely on regular paper. Make it easy on the eyes. Include the header from your blog and some indicator of the color scheme so it looks like a printed piece. Of course, do this only if you want them to immediately run to look at your entire blog, because that's what I'd do in a hiring position. If it's an issues-oriented blog, it could help you. If it's just a place to put various types of writing, play it safe and don't give the name.

If you had time to post links of some of your possible choices I, for one, wouldn't mind giving you an opinion, for whatever it's worth.

They probably just want handwriting samples, so just give them something like this.

...in which you build a clear, strong, and forceful argument, rallies the reader, and shows good writing style at the same time.

I'd also recommend having your verb tenses agree.

*blushes*