I was spoiled by the MySQL timestamp field

As someone who is just getting started with PostygreSQL from years working
with MySQL, it appears that the timestamp data type does not behave in the
way it did with MySQL. I got used to just defining a column as a timestamp
and letting the database throw the latest time stamp in there whenever a row
was updated. Is there anything simular in PosgreSQL? How can I accomplish
something simular inside the database, or am I stuck populating the field in
some manner as in the following example

update blah blah blah timestamp = NOW()

Thanks,

Alan