I usually just use:
SELECT field1, LEFT(field2, 15) AS field2_trimmed
And then conditionally add the dots if needed using PHP:
<?php if(strlen($field2_trimmed) >= 15){ ?>...<?php } ?>
(Instead of just dots, I usually have something like ...Read More which is a link to the rest of the content)
Thanks again though to edcellgavin for showing how to add the dots right in the SQL.... Life is so much easier when you REALLY know what you're doing.
Peter