title says it all

Amazon I assume. I'm a console gamer so, I use Gamestop. Idk if you can preorder PC games there.

Are you just looking for a digital copy?

It won't be available for pre-order on Steam until at least a few months before the release date.

If you plan to order digital download, you should go with Steam, as they have a history of working with TES modders in the past to enable OBSE, for example.

I will probably pre-order on Steam as soon as it becomes available.

Gamestop, Amazon, Bestbuy, etc.

Gamestop or anywhere on the internet.

You can. That's where I preordered my copy (on PC).

digital, and steam is my preferred one. oh well, will wait for steam to get it then, didn't know they waited so long.

Steam will have it just be patient the game is still far from the release date.

Go for Steam. Mods work on both Morrowind and Oblivion from Steam, but do not work on other services.

And going from what's happened for Oblivion, FO3, and New Vegas already, Valve will probably help make the inevitable SKSE* compatible with the Steam version.
*SKyrim Script Extender

If I pre-order from amazon to get the map that comes with the retail copy, will I be able to download the game from steam in a couple years if I lose/break the disc in that time?

It's not yet confirmed, but I think it will be likely.

When asked whether all the retail boxed PC discs would be using Steamworks DRM, Todd answered somewhat cryptically, "We like Steam."