I really enjoy the way fallout 1/2 are described so I would like to try them out, but I haven't the slightest idea about where to get them from.
I would prefer to get it from a store, because I would like to refrain from giving credit card information.
All ideas, however, are accepted anyway.

GOG sell cheap downloads of classic PC games.

But if you want to help Interplay with their finances in relation to the Fallout MMO they're developing, then I'd suggest you buy the Fallout trilogy box set. You'll get it for about ?10/$15. That includes Fallout 1, 2 and Fallout Tactics:Brotherhood of Steel. Fallout Tactics is a spin off, and breaks away from the style of 1 and 2 a little, but still enjoyable

I'd say take a look online for that, some local gaming stores still stock them on occasion, here in the UK at least. But online is your best bet

Try Gamestop, they have almost everything...Or Amazon...

In the UK, you can often find the White label boxed set in Game... But thats a buggy collection. Make sure you get Killap's unnoficial patch.

http://www.gog.com/en/search/sort/search/fallout.

Wait...fallout MMO?

It's in development. See:

http://fallout.wikia.com/wiki/Fallout_Online_FAQ

Know the game before you buy it; Its a fantastic series, but might seem a bit alien.

4 minutes of general wandering and combat:
http://www.youtube.com/watch?v=xSfwDgFeIHU

General dialogs from F1 & F2:
http://www.youtube.com/watch?v=RW8TNY9W_2E&feature=channel_page
http://www.youtube.com/watch?v=1yA8IMXOsDQ&feature=channel_page