IFFSnooper was originally designed as a tool to view the contents of a Sims 1 IFF file, but grew to permit resource export and reassembly. By combining parts from different files it is possible to create a new IFF file for the game, if you know what you are doing.
To save a folder full of resources select
Export -- Disassemble
To convert a folder full of resources into a binary file select
Import -- Resources
It is quite possible to create an IFF file which won't work at all if you leave out some vital piece. Consider IFFSnooper as a research tool, not a full-fledged object editor.
Making new IFF files