I was on an e-junkie forum when it hit me how relevant your signature can become to you making money online. E-junkie helps you sell online.
Your signature gives you the ability to leave a digital footprint all over the Internet. This digital footprint can greatly increase the amount of inbound links to your website or blog in a organic and painless way. Whenever you sign up with a particular forum you would add your unique tag line in your signature. Your tag line would then be converted to a link pointing to your website or blog. Whenever you participated/posted in that forum your signature containing your link would appear at the end of your post. Each time you left a comment, started a new thread or post you would have another link pointing toward your website or blog.
You could and should do the same thing in terms of creating a unique tag line and link in your email signatures. Whenever you sent an email your tag line and link would appear at the end of your correspondence automatically.
Your links could be used to direct people to your sales page or affiliate link. Increasing the likelihood that you'll make money online from your signature.