Audacity is an open source audio editing program that can be used to edit audio files including files created using the iTalk voice recorder.  To download this software see:
http://audacity.sourceforge.net/
(when downloading Audacity be sure to also download the LAME MP3 Audio encoder)

Audacity can be used to combine multiple audio files.  This is done as follows:

1. Open Audacity
2. Open all files to be combined into a single audio files and identify the audio file to which others will be added
3. Choose Edit > Select All for a given audio file
4. Choose Edit > Copy
5. Go to the master audio file (the file identified in Step 2) and Choose Edit > Paste
6. Chose File > Export as MP3

Once audio files have been combined into one file, open new combined file in iTunes and add meta data (see: Adding Meta data….)