I usually just whisk together a little olive oil and balsamic vinegar, with fresh cracked black pepper, and sometimes a little dijon mustard. I use different types of balsamic vinegars for different flavors, depending on what I'm putting it on. Some are sweeter, some are more tart. I don't know what you'd use in place of oil. I think I've seen recipes that used a little bit of chicken stock or citrus juices.