If you can identify the other businesses that service a similar demographic as your business then you've likely found a good candidate for a cross promotion. It's especially easy to set up such promotions if both parties have a similar size audience. A cross promotion occurs when you each agree to send out a promotion supporting the other party's business.
Online these types of arrangements happen frequently. If both parties use an affiliate link to track the number of sales and pay the other party an agreed-on commission, you eliminate any concerns over the two of you having different size audiences or differing response rates to the offers.
I've helped dozens of new online marketers get established by promoting their quality products to my audience. This grows their e-mail list, gives my customers the quality products and information they want, and earns me commissions on the products I promote.