There are several companies out there that will help you create a paperless workflow. Echosign offers a paperless approval and e-signatures with a free version as well as some paid versions. The free version is a great way to try it out without having to put any money up. This low barrier to entry sets their product apart from the competition. See the Echosign Review for more information and screenshots.
Docusign has a similar offering, but with no free version. Docusign offers some additional features and integrates with CRM systems. While Echosign uses a web based interface, Docusign has you actually download the documents that require your signature. Checkout the Docusign Review for more information.
For people who want a more generic solution, digital signatures and encryption give you a way to handle signatures and encryption without relying on a web based service. The downside is that it may take a bit more effort to get setup, but the upside is that you’ll be using a standard technology that works with most email clients on any platform.