The Kindle 2 manual says (section 3.3):
Viewing a Table
Your reading material may contain a large table that is not entirely contained within the screen. To see the rest of the table, move the 5-way controller up or down to bring up the cursor and then place the cursor to the left of the table. Move the 5-way to the right to scroll through the rest of the table.
I don't know if this is also possible somehow on the Kindle 1. Generally, MobiPocket advises against using large tables.