Geographic Distance Queries?

[eluser]Unknown[/eluser]
Hello All,

I have a places model with lat and long, and I'd like to be able to make simple geographic queries for related places, such as finding places within a mile of a given place.

Can anyone point me in the right direction of work that has been done in this area or libraries that might exist?

Thanks in advance to all for helping a noob. I'm new to CodeIgniter but not application development or frameworks. (I'm starting to get into CI for its PHP roots with ease of use and deployment)

Scott