Posting a First Chapter on the web...

If you're doing most of the marketing, then you should probably make a website for yourself or your book. That would be a good place to post an excerpt.

I second having your own website, but it might be worth your while to have someone else build it unless you have mad web skills. Then you have a place to post your first chapter, book trailer, and start teasing future books, etc...

If you're on Amazon, they sometimes let people read a chapter.

If you're self promoting, your own website is essential. Yahoo offers better good hosting for 13/month (domain included) and its easy to use to create your site. If you look at my website (Davisstories.com) you'll see how I organize and exhibit excerpts from my published stories

In my experience, Yahoo is hugely problematic if you have a problem that they need to resolve, or you want to move your domain elsewhere. They never once answered a single trouble ticket I sent them and refused to release my domain when I wanted it moved. They did not return phone calls. They did not, in fact, help in any way, shape, or form. Personally, I would run very very very far away from Yahoo!.

Since then, when I've had other problems with their services, i.e., Yahoo! groups, Yahoo! email, MyBlogLob, etc., I've found them just as unhelpful. After ten emails to them about one specific problem, for example, I gave up since it was obvious that not one single one of their tech support people had read even one of my emails in full. Sure, they now respond to email, but what difference does that make when the service is that bad?

Get your own website, whether you're self-promoting or not. I think every writer should have their own website.