You can juggle pretty much anything, if you can throw it
and catch it. The easist thing to juggle, is oddly enough,
tailor made juggling bean bags, which you can buy
from a number of places. Some people think juggling scalves
are easier, as they have more wind resistance, so everything
happens a bit slower, but I'm not convinced of that myself.
The great thing about bean bags, is when they hit the floor
(technicaly knowns as 'a drop''), they don't roll away, which
is very very handy when learning.
Alternatively, you can make your
own out of balloons and seeds.