Leave off the quotes
$cmd &
$othercmd &
eg:
nicholas@nick-win7 /tmp
$ cat test
#!/bin/bash
cmd="ls -la"
$cmd &
nicholas@nick-win7 /tmp
$ ./test
nicholas@nick-win7 /tmp
$ total 6
drwxrwxrwt+ 1 nicholas root 0 2010-09-10 20:44 .
drwxr-xr-x+ 1 nicholas root 4096 2010-09-10 14:40 ..
-rwxrwxrwx 1 nicholas None 35 2010-09-10 20:44 test
-rwxr-xr-x 1 nicholas None 41 2010-09-10 20:43 test~