use curl instead : curl -v -X POST 'http://<ip.address.of.server>/add' --data "title=foo&text=baz and spam and eggs"
for a post in telnet you need to specify the body of the request like this :
POST /add HTTP/1.1
Content-type:application/x-http-form-urlencoded
title=foo&text=baz+and+spam+and+eggs
If you want to build a query string from a dictionary you need urllib
import urllib
params = {title:"foo",text:"baz and spam and eggs"}
print """
POST /add HTTP/1.1
Content-type:application/x-http-form-urlencoded
""",urlencode(params)