There are many articles online covering getting Sql Server Reporting Services 2005 working on Vista with IIS 7, but none that I found covered the particular problem I was having. Everything installed ok and the configuration manager was giving me all green checks, but accessing /Reports gave me an error about "unable to connect to the remote server" and accessing /ReportServer gave me a 403.1 Forbidden.
While poking around the IIS Management tool I noticed that in the Http Handlers section, virtually nothing was listed for the ReportServer web application. No ASP.NET, no nothing. I clicked "Revert to Inherited", causing it to pick up the settings of the parent site (that had ASP.NET enabled), and everything started working fine. Who knows how the handlers got overridden, but at least it's working now.
EDIT: Also, to fix some other nastiness, you have to follow the advice of "rmeans" here
Without the wildcard mapping you get a fun "For security reasons DTD is prohibited in this XML document" error.
EDIT2: And to actually call the web services via WCF you have to take the obvious step of switching the generated basicHttpBinding to pass the windows credentials, like this:
<binding name="ReportingService2005Soap" ... >
<transport clientCredentialType="Windows" proxyCredentialType="None" realm="" />
<message clientCredentialType="UserName" algorithmSuite="Default" />
but also the totally not obvious step of allowing the client credentials to impersonate, even if you're using a shared data source with a defined id and all that. You add a behavior to the endpoint for the SSRS web service like this: