chemical formulae program

Hi,

I wonder if anyone has any ideas for a freeware program that would allow me to construct chemical formulae (basically 2-dimensional, with bars representing bonds----this isn't a very technical, articulate description, there is a name for this type of representation, but I forget the name----essentially what you'd frequently find in chemistry textbooks).  I'd like a program that would allow me to construct simple representations and then clip them for use in word documents and PowerPoint presentations.  I'd appreciate any help you might give.

Thanks, John