I take:
A multivitamin a few times a week.
Omega 3 (a vegan brand) a few times a week.
I also drink soy beverages that contain vitamins and minerals, and when I workout, I put Emergen-C (a source of vitamins C and B) in my water.
If I don't feel I've hit my daily intake of calcium, I'll take a calcium-magnesium-vitamin D pill.
When taking vitamins, be sure to take into account the enriched foods you eat. If you eat something like Total cereal (100% of many vitamins and some minerals), plus a vitamin-enriched meal replacment drink, plus a multivitamin, you could get too much of some vitamins (fat-soluble vitamins like A and D can be dangerous in excess, while excesses of water-soluble vitamins like C will just wash right out...but make you visit the rest room more often than you might like!).