SBook5 for Mac

From Nitroba:

SBook5 is an extremely fast, AI-based personal information manager for computers running the Mac OS X operating system. SBook5 organizes your information into pages, or entries, with one page for each person, company, or thing that you need to track. Each of these entries can have any number of postal addresses, phone numbers, email addresses, or other information. SBook recognizes the information that you put into each entry and allows you to intelligently manage it.

SBook5 automatically tells the difference between an entry that represents a person and one that represents a corporation, and sorts accordingly. The database then sorts entries as you would, if you only had the time. SBook5's proprietary searching algorithms search in the blink of an eye. Just type a few characters from the person's name, and SBook5 instantly finds the right entry. Don't know the name? No problem -- SBook5 automatically downshifts to full-text search mode, automatically finding all entries that match what you type. Multiple people can have the same SBook5 database open at the same time; when one person saves their file, the changes are automatically reflected in all other instances of the application running on other computers.

Besides incredibly fast search, SBook5 can also dial the phone, print envelopes, mailing labels, and integrate with other applications. And it has an incredibly responsive developer who is always looking for new ideas.