Today we stopped by the Oxnard Beach Park on South Harbor Boulevard, South of Wooley Road and next to the Mandalay Suites Hotel in Oxnard. I was quite impressed with this awesome pirate-themed play area that looked pretty much brand new (we visited on January 2, 2010). The structure is huge and my boys had a blast with it, particularly the 4 year old. There is a larger structure for 5 to 12 year olds and a smaller one for younger kids.
And of course this park is just a short walk to the beach, where we also spent time digging holes, building sandcastles and running from the waves.
The park has a large grassy area, restrooms, BBQ grills, bike paths, etc. Parking costs $1 per hour and I paid it, though it didn't appear as if anyone was monitoring. Definitely worth checking out!