Hey Brad…Not sure if this is what you are looking for but if you sign-up for or use PayPal, you can invoice people using that. It’s free and it’s pretty awesome…and no, I receive no kick-backs from PayPal for mentioning their name 🙂
Another option is if you have Microsoft Word there are quite a few invoice templates you can use. The advantage with that is that since it’s a Word document, you can edit it with your logo, info, cute pictures…the sky’s the limit.
Good luck Brad