Adobe Lightroom is a must for just about every photographer. It is a program with an enormous number of possibilities. You can best describe the software as a photo database combined with an editing program. Using Lightroom you can edit your photos digitally and store them in a structured way in a database. This way you don't lose the quality!
The handy thing about this is that you can immediately add categories and tags to organize thousands of photos. You bring much needed structure to your work. You keep your photos organized per theme and they will be easy to find afterwards. This is a real necessity for every photographer who views life, as a true professional, through a photo lens.