A golf ball gets its distance from the amount of compression/rebound inside the ball that is produced based on the speed of the club head connecting with the ball. Players with slower swings are not able to produce much compression. A ball with a low compression means the ball rebounds better off the club, thus providing some of the missing compression in slower swings.
A low compression ball is simply a softer ball with a core that is less dense than a ball with a higher compression. These balls have a compression of 70 to 80 units--higher units mean higher compression and lower units mean lower compression.
The Srixon Soft Feel is a very soft ball that provides excellent feel that launches high and reduces spin. They can be found at about $20 a dozen.
The Bridgestone E6+ has a low compression core and mantle (layer of material surrounding the core), which helps reduce spin, especially for nasty hooks and slices. You can buy these excellent balls at $27 a dozen.
The Bridgestone B330-RX is an advanced ball built after extensive research and development. "Golf Digest" claims it has the "most intriguing ball technology in years." Be prepared to pay $43 a dozen.