I’ll be attending a potluck tonight and, though I’m not Jewish myself, many of the guests will be. My familiarity with kosher laws being what it is, I’m sure that what I bring wouldn’t satisfy the most stringent requirements, should anyone ascribe to them. But I can make an effort to follow as many as reasonable, especially of the sort about ingredients and their combination. Would anyone have a recipe to share that’s reasonably easy, delicious, and not terribly heavy on esoteric items that I wouldn’t already have at home?
Fruit salad.
There are no unkosher fruits. 
Pasta with vegetables and a plain tomato sauce. No diary.
Latkes, or potato pancakes. Yum!
Or since that might not be that practical, how about pierogies?
But if you cook them in butter, clearly mark them as such. Because butter is dairy even if latkes are vegetarian.
Latkes are a horriffic amount of work though. And they taste kind of gross cold, so you would have to heat them up on site, and then they won’t be crispy after reheating… . So it wouldn’t be my choice for a potluck.
Is the host/ess Jewish? If so, he or she might have some creative suggestions. If not, with no guidelines from the host, I think I’d be inclined to take a less ethnic suggestion in the thread (like Hello Again’s or Annie-Xmas’) just to avoid going through a lot of trouble only to discover two other guests made the same Kosher favorite that I settled on.
Answsering kosher questions on Saturday is not kosher.
I was going to say this. When in doubt, ask the host. I’m assuming if they’re asking you to bring something to a potluck, and they know you aren’t Jewish, they’re not going to insist you have two sets of utensils, cuttings boards, etc., to make a kosher dish, but, whenever attending a potluck of people I’m not that well-acquainted with, I like to get an idea of what, if any, dietary restrictions I should be planning for.
Yes, it is the hostess who’s Jewish. She’s having her extended family in, and they’re ordering food from some carry-out place or another, so I don’t have to be concerned so much about bringing the same thing as the hostess’s grandmother. But I would like to bring something that everyone can enjoy, and maybe learn how to make a new recipe while I’m at it. I’m sure there would be recipe websites that are especially kosher-friendly?
Hummus might be a good choice.
Do you know if they keep kosher? Many non-orthodox Jews in the US do not. If you really want to be sure I would bring something vegetarian and dairy free, because if you bring something with dairy and the hostess buys something with meat, it won’t work. Often I suggest serving dairy if you’re the host if you want to avoid buying kosher meat, but you don’t know what the other dishes are this isn’t a good idea.
If you decide not to worry about kosher, but are concerned about being respectful, avoid ham or shellfish. Many Jews who don’t keep kosher at all still avoid those foods. Frankly, if the host invited you to a potluck and said nothing about food restrictions, I’d be surprised if she was expecting you to try to find something kosher.
Check with the host regarding the level of observance of all of the attendants. If they are very observant, they would not even want to eat fruit salad that had been prepared in a non-kosher kitchen. In that situation, pick something up at a kosher bakery or deli. OTOH, most American Jews don’t follow that level of kashrut, and many will happily eat a bacon cheeseburger. Specifically make sure you know that everyone would be willing to eat “kosher-style” food that was prepared in a non-kosher kitchen.
Perhaps go to a kosher deli and pick something up there?