speeding up COUNT and DISTINCT queries

I'm looking for a general method to
speed up DISTINCT and COUNT queries.


mydatabase=> EXPLAIN ANALYZE  select distinct(mac) from node;
NOTICE:  QUERY PLAN:

Unique  (cost=110425.67..110514.57 rows=3556 width=6) (actual
time=45289.78..45598.62 rows=25334 loops=1)
  ->  Sort  (cost=110425.67..110425.67 rows=35561 width=6) (actual
  time=45289.77..45411.53 rows=34597 loops=1)
          ->  Seq Scan on node  (cost=0.00..107737.61 rows=35561
          width=6) (actual time=6.73..44383.57 rows=34597 loops=1)

          Total runtime: 45673.19 msec
                         ouch.

I run VACCUUM ANALYZE once a day.

Thanks,
max