There are lots of different recipes if you just do a Google search. Most people use vinegar and/or mustard and Stevia for dressing. You can use raspberry flavored Stevia, add some salt, pepper and herbs (I like tarragon) to make it pretty tasty. Some also use braggs liquid aminos or salsa as a salad dressing, but make sure if you try salsa it has no added oil or sugar (organic is usually better). Some are against mixing vegetables so if you use salsa with tomatoes and onions, it's technically "off protocol."
I also used Walden Farms dressings on occasion. They do have Splenda in them, so if you are against that, they probably aren't for you. I got sick of all the vinegar and wanted something creamy once in a while so they worked for me.