Yeah I don't think freezing veggies that have already been fully cooked would give you any nutritional value - and they go so soggy and tasteless. Ok for stews and curries as jaylou says, but not great on their own.
best thing to do with extra veggies is to 'blanch' them in hot water (just for 1 minute in boiling water), then freeze them... When you want to use them, you then cook them fully (obviously for a minute or two less as they're part cooked before freezing!)
great if you have a load of veg that's about to turn - this heat ruins all my fruit and vegetables within days!