For extra va-va-voom in the flavour department, make sure you brown your mince (if using) in small batches in a separate pan so you get good colour on it and the sugars in it start to caramelise. Then de-glaze that pan with a good glug of red wine and add the lot to your sauce. Really boosts the flavour.
A very simple vegetarian pasta sauce is chopping up a load of veggies - carrots, plum tomatoes, red onions, leeks, red peppers and adding enough boiling water (with a spoon of vegetable bouillon) to cover them, then letting them simmer over a low heat for about 2 hours until you have what's basically a thick vegetable jam. Incredibly sweet and lusicious, really lovely with pasta.