"How to move your small business to the cloud?" [Techworld] offers up "what you need to know about cloud computing: what it is, pros and cons, suggested services, and tips for applying it to your business." The article mentions two 37signals products, Highrise and Basecamp.
Highrise for CRM and Basecamp for project management ($24 to $149 per month each, depending on the level of service you choose) both come from 37signals. A number of small businesses we contacted recommended these services for their feature sets and ease of use.
