I use Echosign (owned by Adobe now) for all my clients who I don't meet face-to-face and they do electronic signatures it works that much better sign Adobe acquired them and works perfectly with my Adobe Pro X software. I don't require to meet my clients who live too far to meet with me. I use Goto Meeting to video conference. I only accept faxed signatures temporarily, if I have a client who prefers this to an electronic signature. They have to send me 2 copies (both signed by them) in the mail, then I sign and send back 1 copy or vice verse. It's such a hassle (we still scan it in our system), but some clients prefer this, but I don't start any work until we've both signed if they require me to go this way.
I use to use Docusign, but once we started getting contracts from Aetna, UHC, Cigna, etc via Echosign I switched, and have been very happy. There are tons of electronic signature services, just find the one that best works for you. It's still your contract and as Linda stated you need to put provisions in that state the electronic signature is as good as a handwritten one same with fax.