Try the recipes on this site, also links to more.
http://www.cs.unc.edu/~kupstas/FAQ_recipes.html
Almost any cake can be made dairy free by substituting soy milk or water for the liquid.
For wheat free, you can go with gluten-free recipes. I think there are a few threads on GF cake recipes in the archives. Use the search option in the Forums section to find them.
Theresa 
My boss has severe food allergies/issues so she has to go by the SCD (Specific Carb. Diet) and on top of that cannot have sugar or dairy! Eeek.
She uses Ghee Butter (dairy free), honey opposed to sugar, and almond flour. It should be possible I had to sanitize my entire kitchen this week when I baked her an apple crumble for her bday. I washed the dishes 3 times.. lol.
My son is gluten free and dairy free (wheat and dairy). For butter we use "Earth Balance" vegan "butter" that we get in our health food section at the local grocery store. Smart Balance light (has to be light) is also an okay substitute, but to me the earth balance seems more like real butter. There's also a gluten free cake flour recipe that I found somewhere that works okay. Just a warning - the gf flours are pretty expensive. The most expensive part of making a mixture is the guar gum or xantham gum (works like gluten - without it your flour wouldn't work!). I'll search my computer for the recipe and PM you if you want. I think I might have gotten it from recipezaar.
My easter cake was made completely gfcf and was soooo good. We didn't want to share with my boy, but since he was the reason we made it in the first place we pretty much had to!
I also have a dairy issue because of kosher reasons. So ALL my cakes are non-dairy (parve)
I use smart balance (the green and yellow tub) for butter substitute.
Tofuti non dairy sour cream and their non-dairy cream cheese is fantastic. And non dairy soy milk.
You have to be careful because some products that are labeled non dairy have a dairy dirivitive in them. I forget what it's called. So, to be absolutely certain, I check if the product is kosher and if the kosher sign has a letter "D" next to it, that sais to me that it's dairy. TRY TO USE ONLY KOSHER PARVE or with "P" label.
There was a thread on here before about this
JanH had posted this in this thread
http://www.cakecentral.com/cake-decorating-ftopicp-6247453-.html#6247453
"Actually, the non-dairy creamers are only lactose free.
Most of the standard or best-known brands contain the protein-rich milk derivative casein in the form of sodium caseinate. For this reason vegans and some vegetarians choose to use a soy-based non-dairy creamer instead"
I am sorry, but I am not able to help you with the wheat free stuff.
Didn't mean to italicize the rest of that!!!! Sorry! Kosher Parve is a good tip for the dairy issues. Keep in mind, though for wheat allergies as well you need to look for gluten free. If it says kosher parve, it can still have wheat! I know, a lot of label checking (and double checking!), but you want to make for absolute sure it's cool. Earth balance vegan "butter" is also a good substitute for butter. It comes in sticks just like the real thing.
Try looking here:
http://www.ener-g.com/Recipe/Default.aspx
They specialize in replacers (egg, dairy, etc...) for cooking. You can search their recipes by the allergens. 
malishka - regular smart balance has whey in it - do you mean smart balance [/i]light? I know that's what we have to use for my son. My mom accidentally got the regular smart balance once....we definitely saw a difference!!!!
Jonahsmom, You're right. I never looked at the whey issue. Never had to. Sorry. Smart balance light can also be used for baking.
I use it as a non-dairy butter sub in my recipe.
Subing is a real pain in the A$$. I always find myself in a store looking at different non-dairy products to sub with. Whole foods is a good place to look and your local kosher store.
Subbing is a total PITA!! It takes me 4 times longer to shop now because I have to double check everything! They have lists on the net with gfcf foods, but manufacturers are changing their ingredients so often you really have to be careful and you can't really trust that the lists on the net are exactly right. Luckily, they also have to put allergen information now so if it contains milk proteins or wheat it should say so. *Should* being the operative word!!!!
My son is gluten free and dairy free (wheat and dairy). For butter we use "Earth Balance" vegan "butter" that we get in our health food section at the local grocery store. Smart Balance light (has to be light) is also an okay substitute, but to me the earth balance seems more like real butter. There's also a gluten free cake flour recipe that I found somewhere that works okay. Just a warning - the gf flours are pretty expensive. The most expensive part of making a mixture is the guar gum or xantham gum (works like gluten - without it your flour wouldn't work!). I'll search my computer for the recipe and PM you if you want. I think I might have gotten it from recipezaar.
My easter cake was made completely gfcf and was soooo good. We didn't want to share with my boy, but since he was the reason we made it in the first place we pretty much had to!
try Tom Sawyer GF flour. It's the only one I use now and I love, love, love it! www.glutenfreeflour.com
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