There's lots of websites with freeware scenery,
- Requires you to sign in but free, and a huge site full of add ons with a good search facility.
- Much the same as the above but no log in required.
- Really good scenery usually can be found here amonst loads of other good add ons.
Of course the 'really good' scenery you usually have to pay to use, I bought some for the airports and area's I use most and its money well spent - add's that extra bit of realism!