How do I make a timestamp column default to current time

Hi,

I'm setting up a simple timecard program and I need a column that
defaults to the current time when a new row is inserted. How can I do
this I tried setting the default to 'now' but all that does is put the
time I created the table in each row! I'm also new to postgresql and if
someone can give me a pointer or two in the right direction I would be
appreciative.

Thanks,

Dave