Just decorated the code with new function...needs to classify it soon..

identica_class_v2.py

#!/usr/bin/env python
# * coding: utf-8 *
# (c) Harshad Joshi, 18 Jul 2011
# Little refactoring done
# ToDo 
# Give it some error and exception handling and make it as versatile as it can become.

import json, urllib2
from urllib import urlencode
import sys,feedparser

def url(a):
	n=urllib2.urlopen(a)
	b=feedparser.parse(n)
	for i in range(len(b.entries)):
	       	print b.entries[i].title
	#del(n)
	#del(b)
	
def url2(a):
	n=urllib2.urlopen(a)
	b=feedparser.parse(n)
	for entry in b.entries:
		print entry.title, entry.id
	#del(n)
	#del(b)

class IdentiCa:
	def __init__(self,user,pwd,apibase):
		self.user = user
		self.pwd = pwd
		self.apibase = apibase
		

	def post(self,msg):
	# connection magic
		pwd_mgr = urllib2.HTTPPasswordMgrWithDefaultRealm()
		pwd_mgr.add_password(None, self.apibase, self.user, self.pwd)
		handler = urllib2.HTTPBasicAuthHandler(pwd_mgr)
		opener = urllib2.build_opener(handler)
		urllib2.install_opener(opener)
                msg=msg.lower()
	# now define a message
		
		if (msg == 'exit'):
			sys.exit(0)
		else:
			if (msg == 'mentions'):
				url("http://identi.ca/index.php/api/statuses/mentions/hj91.rss")
			else:
				if (msg == 'home'):
					url("http://identi.ca/api/statuses/friends_timeline/hj91.rss")
				else:
					if (msg == 'friends'):
						url2('http://identi.ca/api/statusnet/app/subscriptions/32987.atom')
						
						v=raw_input('Enter the id of friend you want to see updates of >> ')
						url("http://identi.ca/api/statuses/user_timeline/"+v+".atom")
						
		
					else:
						if (msg == 'status'):
							e=raw_input("Enter your status >> ")				
							# url encode it nicely and set your own client name – no links in source!
							themsg = urlencode({'status':e,'source':'CollaborativeMicroblogging'})
							# and send the notice
							urllib2.urlopen(self.apibase+'/statuses/update.json?s', themsg)


m=IdentiCa(user = "hj91",pwd = "yourpasswd ",apibase = "https://identi.ca/api")
while(1):
	c=raw_input ("Enter somthing >> ")
	m.post(c)
	

del is not a function, don't use ()'s, nor with while or if statements.
There is no point in using del the way you do because local variables are already deleted when the function ends.
Use elif in your if statements and convert msg to lowercase once:
msg = msg.lower()

@calroc removed del.

Great!
You can also make the if..else chain simpler with 'elif' (and leave out the parentheses)

if msg == 'exit':
    sys.exit(0)
elif msg == 'mentions':
    url("http://identi.ca/index.php/api/statuses/mentions/hj91.rss")
elif msg == 'home':

...