Make your own Meal Replacement

My recommendation is always to derive as much of your nutrition from whole food sources as possible. The key word there is: nutrition. Most people have no idea just how 'dead' most of the food they're eating is. Our modern criteria for food consumption has become "I can digest it and I don't die." That really is pretty much it.
For some of my clients who I just know are not going to fix their diet whether it's due to a lack of will or a crazy schedule I will sometimes recommend a meal replacement powder. Something like Myoplex or Met-Rx. However, if I can get them to do a little chore I normally recommend to make your own. What's in a meal replacement? Protein, Carbs, and Fats. That's it. despite all of the marketing and 300 pound monsters screaming at a mountain or whatever on the box, there are no magic ingredients in these things. In other words, make it yourself. Not only will you save more than a few bucks, but you know exactly what is going into it. What do you need? Protein, Carbs, and Fats. You can also add your own bits and pieces such as fish oils, vitamins, etc. I try to get my vitamins in liquid form (via vegetable sources), and if it didn't taste and look like garbage bag leakage, I could mix it in. Then however, my whole shake would taste like garbage.
Get yourself a coffee grinder from Target ($20) and grind up a bunch of oatmeal to powder. I would try to do several servings at once, then toss it in a ziplock bag. Then fill another ziplock bag with protein. Done. You can even make several single serving packs with smaller baggies.
Of course now that I'm warrior dieting I don't do this anymore, but if you're trying to put on some weight this is very useful.