Unix: merge many files, while deleting first line of all files

Assuming your filenames are sorted in the order you want your files appended, you can use:

ls *.extension | xargs -n 1 tail -n +2

EDIT: After Sorin and Gilles comments about the possible dangers of piping ls output, you could use:

find . -name "*.extension" | xargs -n 1 tail -n +2