I live in Stockholm so if you have any specified questions do feel free to pm or msn me.
Sad to say that hotels in Stockholm are somewhat shabby, not sub-London tho.
Cheapest way is just to thrawl through the internet sites like ryanairhotels and lastminute.com and see what you get. Just watch out for the one called Nordic Light, it's duller than real life in it's most gloomiest. You can always rent a room in my friend suburban flat if you want cheap and Stockholmy, it's not a joke but it should be.
For shopping, start by making a list, 1,2,3,4,5 etc, and just go NEU NEU NEU NEU! the rest of the way you can thrawl through SoFo and St.Eriksplan. Birger jarlsgatan is rather dull actually but if yr looking for nice quality shirts do visit La Chemise. You will probably do NK as well so you can just visit the PK-house right next to and try the shops in there, acne and some other brands are housed. Do not forget the CDG-guerilla store or the new Nakkna store at Medborgarplatsen. I'd be more than happy to make some printable map with highlighted place to shop if you would have any use of that.
For clubbing ? Am not really sure what kind of scene you usually belong to but Kilotin is rather hyped nowadays (
http://www.kilotin.se/gallery for pics of the clientele).
as someone questioned already, when you coming ? summer or fall?