Every small customer-oriented business I've seen starts out relying on standard tools for calendaring and contacts, and establishing policies for tracking sales, prospects, and business relationships of all sorts. And in every case, that approach eventually self-destructs, usually at the worst possible time. That's when organizations either create a custom solution (which itself often falls down at some point) or turn to what's called a customer relationship management (CRM) package like Marketcircle's DayLite.
Using an elegant Aqua interface, DayLite provides a highly flexible and interlinked contact database that you can share with everyone in the company or with just appropriate people. Contacts contain role and relationship fields, and you can attach notes, URLs, and file references to contacts - and if that's not enough, you can define extra custom fields. Calendar events can be linked to contacts and to projects, and you can group sets of tasks and appointments into sets for easier linking. Activities can have billing rates attached to them, and any DayLite object can have a task timer that tracks time and billings. DayLite's opportunity tracking features help you share leads around the organization, identify which colleagues are involved in a given deal, visualize its progress, and forecast revenue. DayLite is a full client-server system that can be accessed over the Internet (good for telecommuting employees) or through a VPN. The server runs on any Mac with Mac OS X 10.2 or later, and records are locked during editing to prevent conflicts. You can synchronize contacts and events with Palm OS handhelds, and those who work with their laptops on the road can take an offline copy and synchronize changes upon returning. It's a complete package and is available only for Mac OS X.