I am not sure of any library that can read corrupted files, but it might be possible to turn an incomplete file into a complete one, adding a phony footer and removing the last file.

Look at the ZIP file format:
http://www.pkware.com/business_and_developers/developer/appnote/
The files in the zip are not connected to each other, so it is possible to read through the file, parsing each file as it comes and bailing out if the file ends unexpectedly:

#!/usr/bin/perl

open( Z, "test.zip" );

sub error {
    print "The file is corrupt.\n";
    exit;
}

sub readstr {
    my $received;
    error() if eof Z;
    $received .= getc(Z) . " " for ( 1 .. $_[0] );
    return $received;
}

sub readint {
    my $received = 0;
    error() if eof Z;
    $received = $received * 255 + ord( getc(Z) ) for ( 1 .. $_[0] );
    return $received;
}

while ( !eof Z ) {
    my $head     = readstr(4);    # PK^C^D
    my $versions = readstr(4);
    # ...
    my $filenamelength = readint(2);
    # ...
    # Parse the rest of this file
    # Until we get an error or go on to the next file header
}

close(Z);
[download]

My code doesn't actually produce a correct footer for the file, but it should start you off.