Parse a Python string literal
Perl, 54 characters

#!/usr/bin/perl -p
s/ |("""|'''|"|')((\\?.)*?)\1/$2/g;s/\\(["'\\])/$1/g


Just as I was posting this, I noticed that it's almost identical to Jan Dvorak's Ruby solution. I'm a little put out by how similar it is, in fact, but I'm going to say "Great minds think alike" and let it go at that.

This program highlights a weird corner case in counting characters in Perl scripts: By my reading, the presence of single-quotes in the script means that I need to count the -p option as two characters towards my total. Typically, when computing Perl script sizes, the initial dash character on the options is considered to be free, on the justification that it can be bundled with the -e that introduces the program proper ... but then you also have to account for any extra escapes you need to enter the script on the command-line. The single-quotes require lots of escaping, so to avoid that penalty I have to count it as a script run from a file, and therefore I get the #!/usr/bin/perl for free, but not any option characters. It's a little confusing.