How long do I have to give my ex-girlfriend to move her stuff out of my house in Nebraska? Her name isn't on anything. I have changed the locks already. She hasn't lived there for 2 weeks but her stuff is still there and I want it out.

You broke the law by changing the locks, if she lived with you for over 30 days.
Friends, family, and lovers are often a grey area when it comes to the law, however, and it depends on what the ousted person does or what a particular cop does if called. (Also you don't say if she lived with you or in a house you own elsewhere.) But mostly they are considered a tenant, like any tenant.
Whatever happens, do NOT put her things out on the lawn or the curb.
Unfortunately you are liable for them throughout the eviction process, even if you have to put them in storage.
Send a written 'notice to vacate within 5 days for non-payment of rent' (IF she hasn't paid rent, even if she never had to pay rent) to her at that address. Then follow up with filing for eviction at your courthouse.

Since this is a legal question I moved it from the Relationships forum. You MAY have broken the law by changing the locks. It depends on whether you changed them after she moved out or to prevent her from entering.

If you changed them after she vacated, you are OK there. If not, you may be guilty of an illegal eviction which could open you for a lawsuit.

In any case, you need to send her a letter (preferable certified), giving her some time to remove her belongings. I would suggest that you give her 2 weeks to arrange for a date to pick them up. Tell her that if arrangements are not made you will dispose of her belongings as you see fit.

My son changed them after she left. She had left her stuff there for 2 weeks. But it has been taken care of since this post. She brought some friends and got all of her stuff out yesterday.