Twitter can be used as a great promotional tool (even to run a contest). EVGA is holding a contest to twitter followers. You can enter the promotion here. It’s a great idea to build up your followers by offering a prize. Perhaps it’s something your business could consider.
Your newsletter could also be used as a promotional tool for clients. I was thinking that I usually end up cross-marketing people I know. I thought it would be a good opportunity to add a “featured client/vendor” on my newsletter I send out typically about once a month. The client/vendor would be able to do a write-up for their company. If any of my clients are reading this (because I know I linked this blog on the latest newsletter), let me know what you think about this idea. I send out to about 20 people across the Americas.