I carry a Crank Brothers multi 17 tool with me when I ride. It's got most of what you need to if you have a problem on the trail. There are several comparable brands that offer the same basic features at a reasonable price.

For the home, a good starter kit is the type offered by most the major online stores. It will contain most of the basic tools you need to work on your bike. There are several different branded names, but they are the same kit. Pricepoint, Cambria, Jenson, Performance, etc all offer this for around $45 regularly. Basic starter toolkit at Performance. Granted these are not professional quality tools but they get the job done and like I said, it is a good starter kit.