Hmm, a quick package search doesn't give anything like a single, standalone utility.
On the other hand, it shows that there's an appropriate Perl library, and it's easy enough to whip up a quick perl script. Something like:
$ sudo apt-get install libmime-base32-perl
And then a script like
use MIME::Base32 qw( RFC );
undef $/; # in case stdin has newlines
$string = <STDIN>;
$encoded = MIME::Base32::encode($string);
$ echo -n "hello" | ./base32enc.pl
The fairly sparse CPAN entry is: http://search.cpan.org/~danpeder/MIME-Base32-1.01/Base32.pm
So, a minor change will let you do decodes, also.