For a few people to use? or for an entire organization and forced through policies?
For a small organization where everyone would change their email signature themselves or have an admin do it for them.
If we had the html for one email signature it would be simple to create a script that would create the individual email signatures.
For a relatively small group of people, most companies we work with just have one decision maker create their own, then distribute it to everyone else.
The decision makers usually can't figure out how, so we (IT) hold their hand through the process.
Use their e-mail program of choice.
Do it in HTML.
Use standardize fonts (This doesn't mean don't use fancy fonts, it means use fonts that are likely in most OSes.)
Send it around with cut and paste instructions, asking each employee to edit the Name, Title and phone extension accordingly.
For groups under 25, we just do it, it's faster for to just do it than to teach 22 people about signatures. 🙂