There is always the_excerpt(), but that does some pretty specific stuff (e.g. adding paragraph tags, adding […], not respect the more comment, use the saved excerpt…). Advanced Excerpt is pretty good at customizing that.
If you want to get real simple though:
<?php $content = get_the_content(); echo substr(strip_tags($content), 0, 130) . '...'; ?>
Change the … to
and you’ve got an even better snippet. 3 dots (periods) is not the same thing as ellipses.
Instead of substr which may not work in some languages use
wp_trim_wordsfunction instead.