I kept a log in the past for rivers, salmon, etc. Now my web site is my log. I've got archives back 4 years. It was really helpful to refresh my memory (which seems to fail me more often ) for the sockeye and silver fishing on lake Washington.
I also briefly printed out the water flow charts - very useful info. I don't get out steelheading as much anymore so I don't keep as good records. One good reason to post fishing reports is it gives you an online journal of yourself and other anglers on particular bodies of water.