Advice needed diagnosing Sienna engine noise

Went to start the swagger wagon this morning and was met with this sound. Yup, the always fun to diagnose obscure noise problem. Basically it sounds like someone's playing a wash board after the engine starts and its pretty loud. It does not seem to go away after letting it run for a few minutes. Here's some details:

1. Sienna w/ 51k
2. Got the oil changed yesterday (this has me suspicious).
3. Checked the oil level and it's fine.
4. Drove it fine yesterday after the oil change running errands w/o the noise.
5. No leaks under the van.
6. No check engine light.

Any ideas guys?

Here's a video of it:

 

I'm thinking it's either the serpentine belt or a pulley.

 

It was oil spilled on a the belt during an oil change...

 

serpentine idler pulley or pulley.