Bring your own pasta. Another idea is to send them a recipe for spaghetti sauce such as this one and bring your own pasta.
At a potluck. Potlucks are perfect because all you have to do is bring your own dish and you know you will have something to eat. If you are really sensitive, dish up right away so that you know it doesn't have wheat (or other things) in it. I like to bring Thyme Chicken to potlucks.
Have people over to your house. This is the perfect way to share a meal with others. May I suggest, that unless you have gluten free baking that is unusually good, it might not be a good idea to bake and share gluten free stuff. Those gluten lovers would be on to you! I try to stick with things like this pesto salad that I can just make gluten free pasta and split the ingredients into two. Or I make something like this teriyaki chicken that is naturally gluten free.
Bring your own pizza to a pizza party. On more than one occasion we have been invited to a pizza party. My kids are dairy free, and I am gluten and dairy free so this is a big problem. Until I started BYOP. Bringing my own pizza. I just put it in foil, and bring it in a small cooler. Then I whip it out at pizza time. It's a little weird, but is nice because then you can "partake" without getting sick.
Ask if you can do a potluck and bring some food. If someone invites me to dinner, after thanking them profusely I bring the news of my food intolerances. One thing that I may do is suggest making it a potluck where I bring something that I can eat to share. This generally goes well. I have even brought over the bulk of dinner. This is something I like to bring: Pork with Grilled Apples.
Bring food just for you and talk to them about it. At certain social gatherings I have even talked to them before hand and just brought my own food. For example, coming over for thanksgiving and just bringing similar things that I can eat. It's a bit awkward, but works.
Give someone a recipe you can have that is naturally allergy-friendly. When I had a baby people graciously wanted to bring something over for my family.My friend had a good suggestion, which was to send out to people wanting to bring a meal 4 or 5 recipes that my family can eat (which don't have too unusual of ingredients). Some ideas are: porcupines, chili, thyme chicken (see above), ham soup and mexican haystacks.