I'll explain with megaupload site

class-map match-any BADURLS
 match protocol http host *rapidshare.com*
 match protocol http host *rapidshare.de*
 match protocol http host *4shared.com*
 match protocol http host *mediafire.com*
 match protocol http host *sendspace.com*
 match protocol http host *hotfile.com*
!
!
policy-map BLOCKURLS
 class BADURLS
   drop

And on the interface you prefer you apply this with

interface wan
 service-policy output BLOCKURLS

Change the string for the msn servers and skype ones

The fact is that there is no spoon, go and block

https://Login.live.com or just as I said live.com http access and nobody will be able to login to msn messenger

I get the login url from here: http://support.microsoft.com/kb/927847/en-us

And do the same with https://login.skype.com

or do this

match protocol skype and drop it in the policy-map

Hope this works for you.

Another useful tip when blocking things like MSN, is to match based on the user-agent string.

For example, all packets sent by Windows Live Messenger (MSN) contain a user-agent string of "Live Messenger" in the HTTP header. You can match user-agent strings using the MQC like this:

class-map type inspect http match-any NO_MSN
  match  request header user-agent regex BLOCK_MSN

You need to have a parameter map (called BLOCK_MSN in this example) that contains the regex for the user-agent you're blocking ("Live Messenger" in this case). Then you create the appropriate policy map to filter matches to the NO_MSN class.

Do a search for user-agent and the program you want to block and you should find links to sites that will tell you what user-agent strings to filter.

Hope this helps, Josh