Say file1.txt had the contents hoover Greeble NI POP and file2.txt had the contents bork Bork BORK Interleave them with % paste -d '\n' file1.txt file2.txt > blarg and get hoover bork Greeble Bork NI POP BORK
hoover Greeble NI POP
bork Bork BORK
% paste -d '\n' file1.txt file2.txt > blarg
hoover bork Greeble Bork NI POP BORK