Signaturely - Super simple eSignature software
WiseStamp - WiseStamp allows you to easily create and implement slick and unique email signatures for your business.
Woleet Sign - eSignatures secured by Bitcoin
NEWOLDSTAMP - Email signature generator
HTMLCSS to Image API - Convert HTML to an image (jpg, png, webp). Renders images exactly like Google Chrome. Works with PHP, JavaScript, Ruby, .NET and more.
Sigstr - Email signature marketing