What can I use as a replacement for cumin? I've just run out of cumin and rather than go to the shops for more I wonder what I could substitute for cumin?

I'm making a lentil soup, which calls for sweating onions and the finishing the onions with cumin before adding the stock.

What can I use instead for variety or desperation?
The problem is that a lot of substitutions are based on what you have on hand.

For instance, I have both liquid smoke and smoked paprika, both of which would add that smoky quality that people associate with cumin.

We also need to consider what other ingredients are going into the dish.  I have spice blends that contain cumin in varying degrees (garam masala, taco seasoning, a rub for ribs), and if they contain other ingredients that I might be using anyway, I'd consider replacing all of them with the spice blend.