I'd like to make a reeses cake but I don't know how to make a peanut butter filling (I don't want to use straight peanut butter) I also thought a hazelnut filling might be nice instead of peanut butter. Does anyone have any recipes? I would greatly appreciate them. Thanks.

There is a peanut butter filling here on CC which is great. I use it all the time.

If you want a hazelnut filling you can use a jar of Nutella as filling.

Here is a recipe I have posted that really is delicious.
http://www.cakecentral.com/cake_recipe-2316-Peant-Butter-Cup-Filling.html