Arrggghhhhh, ruddy stickers!

[Miketendo]

IMO, that collection is a total ripoff.

[Coxy]

I haven't been inclined to buy the collection but I swear by warm water and talcum powder on cardboard or plastic. Do the best you can with the warm water and then rub talcum powder into the remaining mess as hard as you can (not hard enough to destroy the item obviously) and then continue to use warm water. Persevere and you should have excellent results.
Also talcum powder doesn't leave the smell of WD40 or white spirit either

[F-zero]

It's abit late now but next time use a hairdryer on it and that heats the glue and you should be able to peel it off.

I second this. Works a treat.

Another recommendation, i've removed 20 year old tape with this method.

[chewy]

Lighter fluid on plastics. Never try to remove stickers from cardboard boxes anymore, I have ruined the few that I attempted.

[killbot]

When I bought Band Hero for the DS, HMV had put a massive sticker right around the cardboard box which was impossible to get off without tearing the box to shreds. I took it back and they exchanged it for another without a quibble.