How to get the url of a .nupkg file?

The URLs are typically in the format:

http://nuget.org/api/v2/package/PACKAGE_ID/VERSION

For example, for WebActivator:

http://nuget.org/api/v2/package/Microsoft.Web.Infrastructure/1.0.0.0

If you just want the latest version of the package, leave out the version number:

http://nuget.org/api/v2/package/Microsoft.Web.Infrastructure/