I used to use Mastercook when I used Windows. Now I use MacGourmet. I recommend both of them
During the first part of my pregnancy I was so grossed out at the thought of food that I started using Menus4Moms too. I only use it to get ideas. Some weeks I'd use all of the recipes. Some weeks I'd only use 1 or I'd browse through the archives to find something better. Most weeks I'd alter to make the recipes fit our family and our food restrictions. Since they only give 5 days worth, I'd use a few of my own as well. Now that I'm feeling better, I'm bringing back in my regular recipes.
ITA about getting cookbooks from the library. I have the Whole Foods Allergy Cookbook out from the library right now
I'm also using doortodoororganics.com for my food delivery, so I am planning my meals based on what comes in my weekly box. When I did this with Menus4Moms, I mostly used the stuff in the box to substitute for the sides that she had planned. I get an email the Friday before my box comes (it comes on Wednesday) so I have plenty of time to plan.
FWIW, I actually prefer to leave my options open, so I don't plan which day I'll do each meal. The only time that days are loosely planned is if I'll be using the leftovers for a meal later in the week.