To all re. must-have scenery addons

I was wondering if some of you might give me some advice re. scenery addons. I recently read the post about the YBCS freeware scenery and gave it a try. I found it very frame rate friendly and very enjoyable (still flying around there) so I was wondering if anyone would care to post some other scenery that they found very frame rate friendly that gave them some considerable enjoyment.1. I do not have a top end system so I am looking for scenery that doesn't bog down the frame rate.2. I don't have a lot of room on my hard drive so I am looking for what you might refer to as "must-have" scenery.3. Being Christmas and all (oops, maybe I should be politically correct here, disregard those first four words...I'll start point 3 again)3. Being the-Man-who-died-on-the-cross-for-us-mas and all I'm a little tapped out financially, so it must be freeware.Would anyone care to give some suggestions?