There exist a number of compositions created to help create a better sound in programs with limited instrumentation while still maintaining musical integrity. The idea behind these arrangements is that, essentially, all band arrangements can be broken down into 5 parts plus percussion.
When you open these arrangements, you have part 1 through 5 each arranged for multiple instruments. Part one is available for Trumpet, Clarinet, Flute, and Violin, Part two for Trumpet, Clarinet, Flute, violin, viola, Saxophone. etc.
The advantage is that you don't have to crash and burn if you have a year without clarinets. You can still cover all the parts and have a good band sound. You can also use this to strengthen week sections by having other sections play the same part. I cannot stress how useful these arrangements are.
The main disadvantages are that the parts are written in general, and not specific to instruments. The harmony is also only 5 parts thick, but that's still a thick sound.
Flex-Band Series http://www.halleonard.com
This is the best series of flexible arrangements available that I have ever seen. They have a great selection of both concert, march, and pop tunes available, all of which are high quality.
Build a Band Series http://www.barnhouse.com/
This is also a great series, though I 've not found them quite as good as the flex-band series.
Rubber Band Arrangements http://www.rubberbandarrangements.com/
This is a site that takes this same concept and applies it to beginner band. They also have a first semester workbook. Each arrangement comes with "virtuoso" parts to challenge beginners that are pushing ahead, while still using the same songs as the full band. These arrangements can be repetitive, but they are built with building block segments that help make learning the songs easier.
First Year Jazz Charts Collection - http://www.alfred.com/
Alfred publishes Jazz charts with a similar concept. They are built to be played by a full big band, or with reduced instrumentation. They also come with alternate parts for flutes, and french horns etc.