I am writing this not because I am an expert, but because I am in the midst of dealing with a picky toddler. Before I had kids, I had wonderful visions of the healthy mom I would be one day--making sure my children would eat an abundance of organic vegetables. I didn't take into consideration that toddlers actually have opinions. And they throw tantrums. How in the world are you supposed to make a kid eat something they WILL NOT eat?!
Here are some things that I have tried and have been successful MOST of the time (I have found what may work one day can definitely be a flop the next day--kids can be very unpredictable with food).
Homemade
Garden: Right out of the garden is best. My toddler had SO many tomatoes this summer...
Soup: frozen veggies, pasta, broth, beans, seasoning, and sometimes chicken. Simple and successful 95% of the time.
Dip: find something to dip the veggies in and it makes it more fun. At our table, this only has about a 50% success rate, but it adds variety to the mix.
Veggie Pizza: either hot or cold, call it a pizza and it has a better chance of working. If it is hot, this works 90% of the time. To mix it up, I like to make cold veggie pizza as well (see this post).
Shredded, Pureed, and Cut (very small): if it is easy to eat, there is a higher chance my kids will eat it. Bite-sized pieces always go over better in our kitchen. Pureeing works pretty well too because my toddler can't pick out or around the veggies. See pictures of "Green Eggs" below.
Smoothies: one of my favorite ways to get greens into my kids. My toddler has become more picky with smoothies and it just depends on the day, but my 1-year-old loves them!
Juicing: I haven't done a lot of this lately because I have been busy and lazy, but this is an AWESOME way to get nutrients into any human being regardless of age.
Baked Goods: zucchini bread and carrot cake are good examples of "hiding" vegetables. It's a good method to boost nutrition, but it's wise to teach them to recognize, eat and like vegetables as well.
Packaged
Pouches: Putting baby food in pouch form has been a great invention. My toddler recently has become more picky and won't always eat the ones with veggies in them, but it worked for a long time. In general, he loves pouches.
Bars: There are SO many bars out there. My toddler will eat them about 70% of the time and I try to buy ones that have veggies in them. See picture.
Drinks: Lots of refrigerated juices have options with veggies in them. My toddler likes green juice more than I do, so this is a great way to get something healthy into him.
Yogurt: I appreciate how Stonyfield puts veggies in some of their products for kids. See picture.
(I realize some of the nutrition is lost in packaged foods, but some is better than none--and let's just face it, sometimes I'm desperate.)