Best way to measure Spaghetti/Linguini portions?
Italians weigh it and it's really the only fail-safe way.  Using a kitchen scale with a big bowl on top should work for just about any pasta shape.  40g for a small portion, 100g for a big plate full.  Cooked volume will depend on the type of pasta, but with spaghetti for example about 55g of dry will produce about 1 cup of cooked spaghetti.

This agrees with @Martha: 2oz = about 57g and 1 cup cooked sounds like a reasonable serving size.  Even if I would eat more :-)