Hi buddy!
I'm no pro myself, but after quite some surfing on the net (acoustics forums and the like), i've come to the conclusion that for stopping sound from leaking out the following might help:
1) mass (physical mass between you and neighbours), especially on bass frequencies-they're much harder to tame
2) phisically decoupling sound sources (avoiding sound transmission through solid objects) i.e.: monitors transmit sound (vibration) to monitor stands, stands transmit to floor, floor transmits to neighbours-so for example, very thick padding might do some good between monitors and stands, and between stands and floor
I would warmly recommend a good pair of headphones-a good investment anyway, as you will always find a use for it in your "studio".
As for rugs and blankets, they will only stop primary reflections (unwanted reverberation,etc.) but i doubt they will do much to avoid leakage,especially on bass frequencies.
That said, you might try:
http://www.acoustics101.com/
It's actually more on "tuning a room" for proper listening (flat response) rather than real soundproofing, but you might find some things useful anyway,
such as monitor placement etc.
Try a googlesearch for similar subjects, you'll get a lot of response!
There's also a lot on do-it-yourself projects for sound absorption.
Also, try this:
http://forum.studiotips.com/index.php
Hope it helps-don't stop reading!
