Any resource for what Android version in a phone?

Is there a resource or link that compares the version of Android in the various Android phones, i.e., version 2.0 versus 1.5, or whatever?

 

Yep, and 2.0.1 is even better.

But I don't have an Android phone yet and do not exactly understand if you can update the OS yourself, or have to wait until a manufacturer provides it, or whether the hardware for all Android phones supports all current and future versions of the OS.

I read somewhere that the Motorola Droids have version 2.0, but the HTC phones only have 1.5

I like HTC better than Moto but I would rather have the latest OS and don't know if it can be put on an HTC phone.

Do carriers impose any limitations on which OS you can have?

Sorry for the noobie questions.