Twitterup is a very flexible wordpress plugin which lets you to tweet while you are blogging. You will be tweeting automatically while you are using your wp blog.
Twitterup will post tweet for you when you create a draft, edit draft, publish draft and publish post. You can customize these options as well for tweeting.
The link you provide for your tweet can be shorted by services like tinyurl.com, is.gd, bit.ly or snurl.com
This is a great plugin to connect your wordpress blog/site with your twitter account.