These are mine:
Entertainment book discounts - Booked HRH for August at $125/night the first week of January. All were gone before the month ended. Became aware of Universal's pass promo (ending on the 23rd of Feb) and saved a ton in passes for 7 days. Overall, I saved a lot more than I would have had I purchased their APs.
Selling on Amazon.com - Just picked up a book during my public library's sale for $1.00, brand new, listed at $112! Bought an older one for $0.25 selling for $80.00!
Onsite resort codes; comparisons between LOS, APs, etc., searching airline websites.
With all the tips, I have saved well over $1,000 in vacation expenses this year.