I keep a ReefLog on web (for self use only), which is basically a diary of all Reef Keeping Events for month, to include:
Test results
Water Change Dates
Additions/Losses (Both very rare)
Purchases
Needs/Wanna haves
Posts on 3Reef I think are important enough to keep on hand for future reference.
(Both for main tank and Nano)
And of course, pics, pics pics...
Send PM if you wanna see...
Scott