Here’s a quick and dirty comparison of ESRI’s ArcWeb Public Services and the Google Maps API. Both are free to use and offer developers a way to display geographic data via the Web.
Walt has a nice quick look at the features of both ArcWeb Services and the Google Maps API. In response to Walt’s comment:
Anyone with space on a cheap shared host can use Google’s API, but without SOAP services it’s difficult to use ESRI’s product.
He should have a look at Andrea Rosso’s blog where he shows you how to use PHP and Perl with ArcWeb Services and Sean Gillies’s post on using Python with ArcWeb Services. Of course it is still SOAP, but almost any website hosting service gives you access to Perl, PHP or Python.