First I'd like to address the other comments. They are correct if you present yourself as a professional photographer. While it may sound "snooty," it's true that you can't properly do a wedding unless you have some serious glass. You should have a collection that gives you 17mm-200mm and f/2.8 along that entire range. Prime is always better, but a 17-55 paired with the 70-200 would suit nicely. If flash is allowed during the ceremony, I wouldn't use less than 3 speedlights. One is a must for any situation. There is also a reason that many wedding photographers are using full-frame cameras and not entry level. The lenses will only get you so far, the camera needs to be able to make up the rest with quality high ISO.

If you're not getting paid and it's a favor, then that's a different story and you should be finagling some rentals. I would recommend explaining to a bride the need to have the proper equipment and propose the couple fronting the rental costs of an appropriate lens.

Indoor Wedding

For $100, you can have yourself a couple lenses that give you wide apertures and you should toss in a hotshoe flash as well. This would give you the opportunity to practice with glass that is more appropriate for weddings, will net you the much needed faster shutter, and I'm sure the bride would appreciate it as well.

Outdoor Wedding

For an outdoor wedding, you'll be battling the opposite end of the scale: harsh sunlight. With impossible luck, you may have a very thin layer of clouds as a natural diffuser and not need anything else, but you'll more likely have to fight the sun with more equipment. I'd pick up a good book on outdoor lighting. "Captured By the Light" by Ziser is a great book on wedding lighting and explains in good detail what to do. The gist of it is needing a couple flashes for a ceremony with light stands and remote triggers. This will let you control the light while working with the sun. You'll still want a constant aperture zoom lens so you'll have your full zoom range without worrying about the effectiveness of your flashes.

Otherwise, if you're looking for a straight answer to your question, you won't find one. If there was a lens that could suit wedding photography for $600, there would be a lot more wedding photographers. For that budget, you're going in ill-equipped and 2 minutes into the ceremony you will be thinking of excuses for the bride. We're not being rude, we're just being realistic and are speaking from experience. With all of the equipment and time that goes into wedding photography, $1k/wedding is barely breaking even.