Mt Hood is an excellent climb with an exceptional payout at the end. The summit views can show you many of the surrounding volcanoes. Be warned, the beauty brings with it a huge crowd. Finding yourself alone in this peak will be nearly impossible. Be prepared, be skilled with your gear. Too many people get injured and die on this peak.
Mount Jefferson's Southwest ridge is a formidable one day goal. Achieving it took a lot of gumption, navigation skill and a general sense of just being in the moment. A more standard route using the south ridge and a two day attempt may be a more stomach-able goal for many. However, I never like it easy.
South sister is as straightforward as a mountaineering experience can get. There is a trail all the way to the top. The only thing that really seemed to get to people along the trail was elevation gain and lack of oxygen. If you are looking to get into the sport, this might just be your perfect intro.