here are some sites about urban planning in Barcelona, and L'Eixample and Gràcia districts specifically... I'm afraid most are not in english but do have some graphic material (photos, maps) that maybe will help you:
since some years ago the City Council has started to free the inner courts of most blocks of L'Eixample, this site is quite good, it will show you which ones are recuperated and which will be returned to the original Cerdàconception (click on Block Interiors):
www.proeixample.com/eng/
check out the City council's official site for the Eixample district and the Gràcia districts:
www.bcn.es/districtes/
also, the Urbanism official site (click on Informació UrbanÃÂstica for gettin' the Metropolitan General Plan, the City Guide with all the streets and particular info on some urban projects):
www.bcn.es/urbanisme/
I did a compilation of buildings of L'Eixample district, from Modernistes to contemporary projects, in this message of another forum:
www.skyscrapercity.com/showthread.php?t=177546
the Barcelona Metropolis
Mediterrània is an interesting on-line magazine -published by the City Council- about urban space and the transformations of Barcelona, there are tons of numbers and are in english, you may want to spend some time looking for particular articles about Gràcia and L'Eixample ... I think I've read some time ago some things about both districts but can't recall which numbers (click on english, then for finding the old numbers click on Archive):
www.bcn.es/publicacions/b_mm/bmm60/index.htm
also you could try to find projects in the Quaderns magazine, edited by the Catalan Official College of Architects:
quaderns.coac.net/q/index.html
and the INDE magazine archives, also edited by the COAC (though these are in catalan only):
www.coac.net/inde/
some more about L'Eixample district:
es.wikipedia.org/wiki/Ensanche_de_Barcelona
the New York to Europe Planning Delegation for the reconstruction of the WTC site visited 5 cities, among them Barcelona, its not focused on any particular district but maybe you'll be interested (PDF):
www.picced.org/pubs/europedelegation.pdf
about Gràcia squares (in catalan but with pics):
www.gracianet.org/la_vila/tomb/
if you're interested in statistics of Barcelona, you could try to contact the DIBA, which is the provincial government of BCN's metro area:
www.diba.es/cartosig/cartoprov.asp
lots of historical plans of L'Eixample and the growing process of Barcelona in this PDF:
www.ub.es/escult/lonas/intro.pdf
the World-Wide Web Virtual Library on Landscape Architecture features some Barcelona projects:
www.clr.utoronto.ca/VIRTUALLIB/LARCH/proj.html
this student's site has some things about art in/and public spaces of Barcelona:
www.spaindev.pomona.edu/barcelona/
about L'Eixample:
www.geographyfieldwork.com/Eixample.htm
www.planum.net/4bie/main/m-4bie-barcelona.htm
a site about public transport in BCN:
es.geocities.com/areaBCN_2005/inicio.htm
hope this can help..