Here are some links that have reference popular songs that can be used for interval training:

This page has sound samples:
http://blog.pandora.com/archives/podcast/2007/10/singing_interva.html

Forum post on another site:
http://www.keepmusicalive.com/interval-help-anyone-t2983.html?

Trainers:
http://musictheory.net/trainers/html/id84_en.html
http://musictheory.net/trainers/html/id90_en.html

2. Root - Minor 2nd
Jaws!

6. Root - 6th
Major 6th = First two notes of the NBC theme.
These are some you can't miss.

Thread here

http://www.keepmusicalive.com/interval-help-anyone-t2983.html?

Thanks guys!

Diminished 6th ascending*: ?????
Diminished 6th descending*: ?????
A diminished 6th is the same as a perfect 5th btw.

http://musictheory.net/trainers/html/id84_en.html

AND

http://musictheory.net/trainers/html/id90_en.html

these helped me a ton in my theory core classes. esp. the 2nd one.

Is it true-
The actual notes of the "NBC Theme" are G-E-C?
Someome once upon a time told me it was for General Electric Company (early, big sponsor of NBC?).

this link should cover it

http://blog.pandora.com/archives/podcast/2007/10/singing_interva.html

First post updated with the links the TB guys provided.

Thanks for the links guys - I'd been meaning to compile a list like this for ages.

GEC are not only the intials for General Electric Corporation, they're very early overtones. Harmonics on the 7th, 9th and 5th frets (on an imaginary C string).