VGA to ADC
Here's the URL for the Gefen VGA to ADC Conversion Box...
Link to Gefen Website
You can order directly from their site, or from any of the major Mac mail order places. If you already have a nice Cinema Display, then it may be worth it, but the quality isn't as good as using a DVI to ADC adapter. However, I have used this and it works well.
If you don't yet have a PowerBook, you may want the 15" or wait for the 12" to get a DVI port (who knows when that might happen?). If you don't have the monitor either, then you can always get a flat panel screen with both VGA and DVI inputs. That way you can still get the 12", which as you know is a sweet computer!