River2 has a page which lets you quickly subscribe to a feed if the "Open Subs Feature" pref is checked off.

It now accepts a url parameter when opening the page, so you can configure Chrome to subscribe via River2 in addition to the other feed readers it supports.

In Chrome's "Edit feed reader" dialog, enter the URL as follows:

Obviously you'd use the name of your server, and your username.

When you subscribe via Chrome it will fill in the URL of the feed where the %s is.

And the URL will appear in the format that River2 puts up.

Very sick! :-)