Apart from the city tour and the High Mountain tour (Aconcagua and/or Cristo Redentor), the Atuel Canyon is another very nice tour, although it takes 12 to 14 hours (depending on the driver) and means travelling some 300 miles, or more. It visits the Nihuil Dam, and from there comes downstream along a beautiful canyon, that is some 1,000 feet deep (this is not Colca, Copper Canyon nor the Great Canyon, but it is still very nice).
The Atuel river has crystal clear waters there, because they have settled down at the El Nihuil Lake. Then you visit the very nice Valle Grande Rafting area, where you can go down the river for 45 minutes at a cost of some 6 to 8 dollars, it is really enjoyable and it is Class II rafting that is no dangerous. After that you will visit a vineyard and winery, and then return to the city of Mendoza. It would rate it as a highly recommended tour. There are no organized tours to the Vallecitos Ski center as far as a know, but it is a beautiful place to visit. A trip on a taxi will cost you some 30 to 35 dollars, including a one-hour stay over there and the trip back. Another very nice tour is the half day tour to Villavicencio, where you will climb the mountain along a winding road (Caracoles de Villavicencio). That would be my fourth priority) The Ruta del Vino tour goes to different wineries where you can taste the wines they produce. Walk along the San Martín park, you will really enjoy it. Do not go during the night, because it could be unsafe.
If you want to visit shopping centers, go to Palmares in Chacras de Coria. It is very nice. And, of course, you should not miss a visit to Las Leñas. Andesmar Turismo has a tour that leaves Mendoza on Friday night about 11pm, arrives at 7 in the morning, comes back at 5pm and arrives at midnight on Saturday. This tour costs some 27 dollars. Last year the ski season in Las Leñas continued well into the summer, because there was a lot of snow. It is likely that this year the ski season will also continue, but check that out with your travel agency. From San Rafael you have local tours to Las Leñas, to the Atuel Canyon, to the Manzano Histórico (Tunuyán, another very nice area). The Galileo Vitale dam is nearby, and as a matter of fact there are a number of dams in this area (including Los Reyunos), where there are good fishing possibilities. You can also go by bus from Mendoza to Uspallata and to Tunuyán or Tupungato, three very nice areas, walk along the villages, and in the case of Tunuyan, even take a taxi to the Manzano Histórico (the historical apple tree) where it is said that General San Martin rested on his way over to Chile, and where there is good trout fishing. I should add that there is a bus service from Uspallata to Barreal (San Juan), near where there are two modern astronomic observatories. But you need to check out visiting timetables at the Barreal tourist board offices. That is also the area where Marlboro runs its wind-driven vehicle races. There is a natural clay racing track about 30 miles long, that seems to be in better shape than many paved highways.