The feed for my url is currently:

http://mysite.com/feed.rss?city=Boston

Where the user can change Boston to another city.

I was wondering if it's possible to customize the default feed reader that lets users provide a city which then changes the feed url. I looked at a few gadgets available (e.g. CustomRSS, Slim RSS Reader etc.) but I need my gadget to look like the default one provided by google (http://www.google.com/ig/directory?q=cnn&root= %2Fig&dpos=top&url=rss.cnn.com/rss/cnn_world.rss) but lets then specify a param (City) as well. If someone could point me to the general right direction, that would be very appreciated. For example, do I need to build this from scratch? Or can I modify google's feed