Generally I work out 3 times per week, and the following is my normal schedule:

Mon - Back / Biceps
Tues - rest / active rest
Wed - Chest / Triceps
Thurs - rest / active rest
Fri - Legs / Back
Sat - active rest
Sun - rest

Last week I started a routine such as:

Mon - Biceps / Triceps / Shoulders
Tues - rest / active
Wed - Legs / Lower Back
Thurs - rest / active
Fri - Chest / Upper Back / Shoulders
Sat - active rest
Sun - rest

My thought process is that if I work my biceps / triceps on Monday, I'm inherently working them again on Friday by doing things such as pullups, "press" exercises, some "pull" exercises, etc. In my mind, this should be working the muscles out twice a week with 3 - 4 days rest in-between. Of course, on Mondays I make sure my bi's/tri's get a full pump and work out to full fatigue (to the point it's difficult to take my shirt off afterward, haha), and on Fridays I do the same to chest and shoulders, but is this efficient? I just started the routine, so not sure how the gains will go yet, but does anyone else do something similar to continue having gains?