Plain ol' Excel spreadsheet (I'm a geek) - Fields: Date, Destination, Activity (climb, snowshoe, ski, backpack, training slog, etc...), Partners, Details (gain, mileage, details, stories, comments, etc...), Drive times (door to TH, and complete drive description), and a column with a running total of my elevation gain for the year.
Hundreds of entries, easily searchable, kept it for years (since 01/01), I email it to myself to back it up once a month or so. I also have a website with the pictures I've taken since I got the digital camera.
I said I was a geek.