Ruby 1.9, 357 355 353 339 330 310 309 chars
d=0
e=[*$<]
e.pop.split.map{|f|f="L\003\003\007J\005\005\007O\007\007Z\007\013S\013\007I\003\003\003\003T\017\005"[/#{f[j=0]}(\W*)/,1].bytes.map{|z|?\0+?\0*f[1].hex+z.to_s(2).tr("01"," #")[1,9]}
k,f,i=i,[p]+f,e.zip(f).map{|l,m|l.bytes.zip(m.to_s.bytes).map{|n,o|j|=n&3&q=o||0;(n|q).chr}*""}until j>0
e=[]
e+=k.reject{|r|r.sum==544&&e<
Note that the \000 escapes (including the null bytes on the third line) should be replaced with their actual nonprintable equivalent.
Sample input:
[ ]
[ ]
[ ]
[ ]
[ # # #]
[ ## ######]
[==========]
T2 Z6 I0 T7
Usage:
ruby1.9 tetris.rb < input
or
ruby1.9 tetris.rb input
