[...]
> And of course ruby's net::http
> does not respect system proxy configuration.

You can make it respect the system proxy configuration:

require 'net/http'
proxy_uri     = URI.parse(ENV['http_proxy'])
proxy_class = Net::HTTP::Proxy(proxy.host, proxy.port)

proxy_class.start('www.example.com') do |http|
    # whatever
end

> I would like to know if there is a way to channelize all the http
> requests through the proxy server specified by path variable
> 'http_proxy' without changing these modules. (These modules are
> separately maintained and making hard changes would make things
> difficult while updating them in future)

So you can probably channelize all your http requests through the proxy_class.

-- 
Anurag Priyam
http://about.me/yeban/