You didn't give much information so I am going to guess that you have a manual trans and that the Jeep has 150,000 or more miles (but with the engine smoking it doesn't really matter what the mileage is -- that engine needs a rebuild regardless.) I am also going to guess that the Jeep is in fair condition. The body rust isn't a biggie but the frame rust is a huge problem. Also, no windshield and a missing driveshaft is a big detractor because it wouldn't pass inspection on the day of purchase -- most people would want that. I will give you my personal estimate as to what you could get out of it from your average car buyer:
6-cyl 4.0L - Somewhere around $1,500. Maybe $2,000, on a really good day.
4-cyl 2.5L - $1,000. $750 would be better.
With the engine smoking, missing windshield, missing driveshaft, and the rust... simply put, that Jeep is a beater car that someone would only buy to get them from A to B temporarily or as a restoration project. I personally wouldn't spend a penny over $1,000 for it with the 6-cyl. If it has the 4-cyl, personally I'd give you $400 for it and use it as a parts Jeep for my '95 YJ but I wouldn't buy it otherwise.
Now for the good news. Spend $250-$300 and get a windshield and the front driveshaft. Maybe spend another $50-100 and replace the piston rings/valve guides. Spend another $150-ish and get the rusted areas patched. Clean it up. Now it's not such a bad Jeep. In this condition you could sell it for $4,000 or more if it's the 6-cyl and $2,500 easily if it's the 4-cyl.
