I have begun the process of organizing some of my music files. In particular I have a number of audiobooks that I ripped from cds. As a result some of those books are hundreds of 2, 3 and 4 minute mp3s.
I found a good tool for merging those files and converting them to aac files. The reason is that enables bookmarks (place holders) to function so that when you change to listening to other things and return to the audiobook you do not need to find where you left off.
Markable by IpodSoft has done the job. It functioned flawlessly for the very short trial period. It is worth mentioning that IpodSoft's Ipod Agent was also a good program when I needed to restore music from my Ipod. Give it a look, it could save you alot of time and headache compared to using applications like Audacity, which is a good app, but not well suited for this purpose.