I've seen a few in field videos on youtube, and I'm wondering if there is some source where I can find a bunch more.

Also, what kind of places would be good to practice approaching? All my friends are nerds so I don't really have a wingman. What places would be good for solo practice?

I'm a 21 year old noobie who has watched a couple Deangelo DVDs, and I want to get out and practice.

Good places for solo practice are everywere; as you can practice anywere were women are. But i would recommend: Daytime - coffee shops, the mall/shops, street (difficult as it can look creepy to girls but asking for directions or something simple is a good way to build confidence), park, beach etc.

At Night - clubs (obviously), bars (obviously), late gym, late shop etc.

If you in school/college/uni - practice on girls in you class, the libary is good place to meet girls as is any specialist clubs. If you work you can try some lines out on the girls you work with and practice small talk but work-based dating can be complicated as if it ends badly, you still have to see them.
Go out and practice as soon as you can, you can only improve. I would also recommend expanding your friends circle as it will open up more opportunities to meet people.