[cd34]

mysql> create temporary table blah SELECT sponsor FROM banners group by sponsor,if(keyword='horizontal','H',if(keyword='vertical','V','O'));
Query OK, 5 rows affected (0.00 sec)
Records: 5 Duplicates: 0 Warnings: 0

mysql> select sponsor,count(*) from blah group by sponsor;
+----------+----------+
| sponsor | count(*) |
+----------+----------+
| sponsor1 | 3 |
| sponsor2 | 2 |
+----------+----------+
2 rows in set (0.00 sec)

Is that what you want?