Is there a wordpress plugin that allows us to show only so much of a post on the main page and then have a link like "read the rest of this entry" which takes them to the archives page? I see many blogs like this but don't know how to do it myself.
There are 2 ways to do this, the way the two previous posters mentioned, with the <!--more--> tag (there is also a button to insert the tag in the WYSIWYG editor), or to change the template. If you change it in the template, it will snip ALL posts, at the same point. (default is 55 chars I think) To do it this way you just need to change the_content() to the the_excerpt() in the main index template. It's probably best to do it using the post by post method, but just thought i'd throw that in there in case it is useful to you.
The more thing is what you need to do. If you are looking out for a plugin, consider this one http://wordpress.org/extend/plugins/evermore/
i have never really been able to get the read more to work either but did run into this plugin today that would prevent your feeds from getting cut off in your RSS hxxp://wordpress.org/extend/plugins/full-text-feed/ now back to looking into why my more button isnt working
Forget everything else, and install 'If you liked that' plugin. You don't have to edit anything and this plugin is jampacked with features too. You can configure everything in the settings menu.
The plugin defines how many paragraphs to show before "read more" and N number of chars it has to contain at least but how to define how many words or at least characters the excerpt will be (by default in Wordpress it's 50 cars).