You can use your gmail id to create multiple accounts. All you need is a gmail id which has dot(fullstop .) in it.
For ex. your id is xyz.zyx@gmail
Now all u have to do is when you register at any site (like facebook) just change the location of dot.
like this.
x.yzzyx@gmail
xy.zzyx@gmail
xyzz.xy@gmail
when you use ids like this site will conseder it as a different mail ids but actually your original id will be registred there.
note: this trick works with some ids only may not work with all type of ids, with my gmail its working. try and reply