Formal:
* Bienvenue chez nous. (This is the most direct and common translation.)
Informal:
* Bienvenue à la maison. (This is a more casual way to say it.)
* Bienvenue chez nous ! (Adding an exclamation mark makes it more enthusiastic.)
* Entrez, entrez ! (This literally means "Come in, come in!" and is a very welcoming phrase.)
You can also add a personal touch by saying something like:
* Bienvenue chez nous, on est ravis de vous recevoir. (Welcome to our home, we're delighted to have you.)
* C'est un plaisir de vous accueillir chez nous. (It's a pleasure to welcome you to our home.)
The best way to say it will depend on the context and your relationship with the person you are welcoming.