In the Snow Leopard mail app, it automatically converts URLs that you enter into links when the message is sent. You don't need to put an http:// in front of the link or anything, just enter the link name. But when you are composing an email, it's hard to tell if you have entered a correct address or not, because the conversion is not actually shown. If you want to show the text that will be converted into links once the message is sent, you can configure Mail to show this.

- Start a new mail message.

- Right-click anywhere in the new message and select Substitutions -> Show Substitutions. It'll pop up a little window like this.



- Check the box next to Smart Links and you are done.

This window is a little odd since there is no button to push to save your changes. Once you make your changes just close the window and your changes will be saved. Setting this will not change any of the links you've already entered, but it will now format new links that you type. Also, it'll work for all new email messages you send, you don't have to do this every time you send a new email.