This is for Mac OS X and requires npm.

Usage:

1. Open a terminal
2. Type bitly http://www.somewebsite.com/needs/to/be/shortened/

The shortened link is now in your clipboard. Paste the shortened link wherever you need to!

Installation:

1. Open a terminal
2. Type npm install request (if you don't already have the request module).
3. Type cd /usr/local/lib/node
4. Type vim bitly.js
5. Now paste in the following code:

var request = require('request'),
		sys = require('sys'),
		link = process.ARGV[2],
		bitly = 'http://api.bit.ly/v3/shorten';
		
function urlencode(str) { 
return escape(str)
    .replace('+', '%2B')
    .replace('%20', '+')
    .replace('*', '%2A')
    .replace('/', '%2F').replace('@', '%40');
}

// prepend http if it does not exist.
if (!/^https?:\/\//i.test(link)) {
    link = 'http://' + link;
}

// urlencode the link and add to params.
var params = 'login=YOUR_LOGIN_ID&apiKey=YOUR_API_KEY&longUrl='+urlencode(link)+'%2F&format=json';

request({uri:bitly, body:params, method:'POST'},function(error,response,body){
	if(!error && response.statusCode === 200 && body)
	{
		var json = JSON.parse(body);
        console.log(json.data.url);
	}
});

NOTE: You will need to supply your own login and apiKey values.

6. Type ESC:wq to save the file and close it.
7. Back in your terminal type vim ~/.bash_profile
8. Paste in the following block of code:

function bitly()
{
bitlyPath='/usr/local/lib/node/bitly.js'
node $bitlyPath $1 | pbcopy
}

9. Type ESC:wq to save the file and close it.
10. Restart your terminal.
11. Type bitly www.google.com.

The bitly link for "www.google.com" is now in copied into your clipboard.