Please advise me on narrowing down to a list of projectors I should consider for my basement where the room size is 17 foot x 17 foot and the height is 7 feet. I need to do ceiling mounting.

Check out the Optoma HD7100. It has a short throw and vertical lens shift so you can keep your screen nice and high.

With a low ceiling you will need an LCD PJ like the Epson HC 400 or the Panasonic AX100u. These are both excellent choices and have many satisfied owners. They have a lot of light and will work well if you decide to mount them the full distance from the screen. The Panasonic is going to be updated shortly to the AX200u.

My theater has almost exactly your dimensions, though the height in 7.5 feet. I just bought and installed a Mitsubishi hd1500 and ceiling mounted it flush. I'm projecting it onto a 106" screen.
No problems at all. You may have to tilt the projector up a little, but I doubt you will have to do any keystoning, I didn't.

Careful or this could become a keystoning vs lens shift debat fast :D

At 7' you would be have a better chance at being happy with a unit that has lens shift but this depends all on your eyes and those eyes of others that will be watching.

the other thing to consider is the height of your ceiling which will result in closer proximity to the unit, so audible noise can come into play.

Any of the popular LCD units will meet your needs with the highest flexibility, things like the Panny AX200 (i would go ahead and wait for this one if you are considering the AX100) the Sony AW15, and many other popular ones here.

If you want DLP, you have a chance at getting better blacks and more "pop" (again this is dependant on your eyes and preference), but these units tend to require some tilting/keystone due to their lack of lens shift.

Depending on your budget and your screen, you could move up to some middle tier DLPs that have lens shift, ala Sharpvision Z12kMII, but the 900 lumens adds the need for a HP screen.

I would never advocate keystone adjustments. My point is that in a same sized room I didn't have to use any adjustments...
The Mitsu is an excelent choice

I would never advocate keystone adjustments. My point is that in a same sized room I didn't have to use any adjustments...
The Mitsu is an excelent choice

Yes, the Mits is an outstanding choice but:

At 7.5 feet, you image is only 14 inches from the floor. In his basement it will only be 8 inches from the floor. Not everyone wants to look at an image that low and it makes it hard to have more than one row.

Are you tilting your PJ and screen?