Don,

My preference for a task like this is to use a logic FET like the FDV302P available from Digikey for $0.39 each ($0.093 in quantities of 1000). It is a p-channel device so it won't turn on when the microcontroller is starting up and doesn't require any resistors like the discrete transistor approach. All you need is one SOT-23 FET and one diode per relay. It is really small.

Depending on what you are trying to do, I would consider choosing a protected FET instead of a relay. It all depends on your application, of course. If you only need to source current from a positive supply or sink current to ground in a DC system, a protected FET can offer smaller size, current limiting, faster switching, and longer life.

- Lee