I would like to warn would-be visitors about a "confusion" around the so-called city passes for the city of Barcelona:
Officially, the only city passes for the city of Barcelona are the ones sold by Turisme de Barcelona --the Barcelona Tourism Consortium-- a public company dependant of the Barcelona City Hall. Its URL address is http://bcnshop.barcelonaturisme.com and in their jargon they call these sort of passes "multitickets". These are the ones available at present.
There's yet another type of passes, sold by Transports Metropolitans de Barcelona (TMB) --the Barcelona Metropolitan Transport Authority-- aimed to those visitors interested in transportation only. The available passes are the called HolaBCN! -free transportation for a period of 2 days up to 5 days - and the Integrated Travel Cards that can also be interesting to visitors, being the T-10 travelcard the most popular and convenient: a multiperson card with 10 journeys for roughly 10€ (not in vain is the most used by Barcelonians themselves).
Lastly, the private company running one of the two hop-on-hop-off bus lines, Barcelona City Tour, has recently launched a card, called iventure, which offers discounts to some attractions, much like the Barcelona Card sold by Turisme de Barcelona above.
Around these, taking advantage of the popularity of Barcelona as a tourist destination, some resellers abroad (based mostly in the Netherlands and in Germany) have piggybacked on the above and are offering online "city passes" which in reality do not exist as such because it's simply a marketing name for the existing products mentioned earlier, obviously with an added fee for the middle-man. It's important to point out this is not to say they're not legal or they're a scam, but it's important to understand the whole background. It, however, adds confusion to the would-be visitors looking for a convenient "one-for-everything pass".