I take Flinstone CompleteI take just a single Flinstone Complete daily. I just posted this in the general pregnancy section too, thought it might be helpful.
If you eat a healthy, normal diet, prenatal vitamins are more insurance than necessity, with the possible exceptions of folic acid and iron (unless you have higher than average nutritional needs due to a multiples pregnancy or maternal health issues or previous child affected by neural tube defect).
What I personally take and think is a reasonable approach if you aren't going to take prenatal vitamins:
A single daily Flinstone Complete Chewable Multivitamin (400 mcg of folic acid)
plus either a separate folic acid supplement or increased intake of dietary folic acid to reach the 600 total recommended (your body absorbs it less well from food than from the vitamin, so probably would need about 400 from diet to make up the difference). That said, natural folate has not been shown to be effective in lowering risks of neural tube defects. And it is most important from 3 months prior to conception to about 6 weeks.
calcium, either dietary (much preferred), or in a supplement to add up to 1000 mg/day
and either a very deliberate effort to eat iron-rich foods or additional supplementation. The flinstone complete contains 18 mg, for pregnancy you need about 30 mg/day (more,obviously, if you start off or become anemic).