In regards to SeaWorld, and this will depend heavily on your circumstances, but don't forget to look at the 1-Year and 2-Year passports that SeaWorld offer, because as well as a good price, there are plenty of benefits that come along with the APs too!
We ended up going for the 2-Year passport last year, which was $149, the equivalent of two on-the-day general park admissions. We went to SeaWorld three times on our trip in Sept '09 (one full day, and two half days), so effectively made our money back already. But of course, our passes will now also cover our May '10, Sept '10 and May '11 holidays too!
So, if you are going again in the next year or two, definitely consider it! You also get the advantage of free parking, 10% off all meals and merchandise within the park, discounts on the other parks should you choose to visit them, discounts on park entry if you bring a friend along with you. And AP holders get to ride the sky tower for free =)
