Pen and Paper for me in a ringbinder at the moment.
Front section has some quick glance pages listing what the batch number is, name, date brewed, date bottled.
The rest of the logs are individual pages in plastic covers listing all the usual:
Batch no
Name of brew
Date brewed
Date bottled
Fermentation temp
Hops used
Yeast used
Quantity of bulk priming solution etc etc etc
I have a macintosh at home and am looking into BeerAlchemy.
Cheers
Steve