Here's my nighlife line up for the moment, feel free to use any of these names to get in free and get a few drinks, it's on me.

Sunday
George Payne Irish Pub (Plaza Urquinaona, 5) Karaoke starts at 8 but it gets full around 10.
DJ Sujinho of NYC "Ice Cream Sundays" at Catwalk (Ramon Trias Fargas 2-4, House, Electronic, Brazilian Funke). Party is on til 6 in the mornin'. Free on Suji's list, go to www.Sujinho.com

Monday
Nasty Mondays at Apolo (C/ Nou De La Rambla 111). Opens at 12:30 and during off season there are flyers you can get to get in free before 1am. I usually ask someone in line for an extra one. This is hipster's paradise. (And it's still fun even if your not one or don't like to label yourself) Young local and international crowd, huge space thats always filled, and it's almost impossible not to meet people and do what may you with them during and after the party.
Earlier in the night George Payne also offers an Open Mic Night for any mucisians, and half the bar staff is so they all come there even if it's their night off, it's a good way to meet some locals.

Tuesdays- Traditionally my night off but....
Crappy Tuesdays at Apolo with DJ Sujinho
or
Roxy Blue(C/ Consell De Cent 294)

Wednesday
Negro Joya is a fun Brazilian samba group that plays currently at Barkeno Lounge (c/Caspe, 17) or there is always Brazilian live music at Gran Foc (C/ Roger De Llúria 23). 11pm

DJ Donnie at Lotus Theater (c/Bailen, 22). Hip Hop music, fills up quick, dancers land on stage from a swing that carries them over your heads in their (I'll be nice and call them "early Madonna" as opposed to stripperesque) imaginative outfits. You can definitely find free passes but if you pay the 10 euros to get in it comes with good drink deals like one or two caipirinhas with your entrance fee. Closes at 4:30 (which is early for BCN so don't show up too late). Julien's list.

Thursday
For a long night...
Bubblic Bar (c/ Maria Cubi, 183) 4 Euro Caipirinhas and people on the street with free shot flyers. (Look for a sexy bartender named Elvis, you'll keep coming back even if he does take way to long to make your drink.) or any of the bars in the neighborhood Gracia (Metro: Fontana). You can botellon (aka buy beers at the market or from the guys who sell them on the street) and kick it in the plazas with every other Catalan til your ready to dance. Then...

Double Trouble at OttoZutz (C/ Lincoln 15), DJ Sujinho and Marco de Soul. Old School hip hop. Otto is fun all weekend it just gets more and more packed as the weekend goes on, three floors so hip hop, rock or house music, whatever tickles your fancy. Be nice to the bouncers they have a lot of clout there so when there is a crazy line if they know or like you, you are in, if not, no chance. It's the kind of place you walk home from during or after sunrise.
-Never wear open sandals you will for sure get glass in your feet!

or

Shoko (Passeig Marítim (La Barceloneta) 36) Finally a club that realizes that girls who call step, touch, step, touch dancing just cause they aren't covering up isn't entertaining. They have three guys, Alvin, D-Max and John who are breakers/street dancers who perform throughout the night. If you can get a name of a promoter you can get a free drink and free entrance before 1 am. Currently, Oliver, but promoters always change. Closes at 3 then Catwalk or Opium are both next door. Oliver's list.

Friday
DJ Josh at Opium Mar (Paseo Maritimo, 34). Massive dance floor, so euro, no casual-I-just-stumbled-in-from-the-beach look. Open til late 5 or 6.

Saturday
... everywhere is packed cause all the tourists are in town, so any of the big clubs or hit up a neighborhood like Gracia or El Born for bars there.

Te pasa lo bien.