If not, is there a way to make a smartlist that doesn't have songs in a certain other playlist?
While zxsix's suggestion will work, and work well (if you pick "Is Not" in place of <>), it could be quite a cumbersome task, as you happen upon a track that you'd rather exclude, to open up the smartlist editor, then trawl through the list of names to find the track, select it, and OK your way back out again.
If you created a playlist to hold those files instead, there's no need to leave the main GUI at all, and so might be easier to maintain...
1st, create your playlist. Then go to your smartlist and open it for editing.
Click on the 'add rule' button., then, from left to right:
Select "Playlists" || "Is Not Any" || "
choose your playlist from this drop down"
Press OK.
Now, next time you hear a track that has no business being in the smartlist results, you have several options:
You can select the track in the list and drag it onto the playlist in the tree.
You can right click on the track, and follow: "Send to... > Playlist >
find your playlist from here and click to select"
You can also right click in the player info display (up top where it tells you what's playing) and use the "Send to..." menu from there.
If you use either of the last two choices, the playlist is added to the top of the "Send to..." menu making it so much easier to target the next time.
Adding a track to your playlist will cause it to be dropped from your smartlist.
As is often the case with MC, there are several ways to achieve your goal, none of them 'right' or 'wrong', only 'what works best for you'. The choice, as they say, is all yours.
-marko.