Can anyone recommend a widget (or service) that I can integrate into my PHP site to prompt a user for their email address upon leaving my site? I'm also open to suggestions as to whether its best once a user first comes to the site to ask for their email or upon leaving the site. Thanks for your time and assistance.
If I'm leaving your site, I want to leave. Bugging me then to give you information there's a good chance I don't want to give you anyway is only going to irritate me. Just put something in the sidebar; if I want to give you contact info I'll see it. If you really have to prompt, do it on initial visit(though I'm not too fond of those, either).