You should look into the concat demux and concat protocol that was added in ffmpeg 1.1. Assuming the codecs are the same you create a file (example mylist.txt):
file '/path/here/file1.avi'
file '/path/here/file2.avi'
file '/path/here/file3.avi'
Then pass that file to ffmpeg
ffmpeg -f concat -i mylist.txt -c copy video_draft.avi
You can use this command to make the list:
ls *.avi | while read each; do echo "file '$each'" >> mylist.txt; done
The linked page has more advanced examples for dealing with issue like different codecs/formats.