What would be the best way to collect data in a form on the main page of a wordpress installation and then display that data later? Is there such a plugin? I'd like to avoid allowing users to log on to the admin part, just have them enter data directly on the front page.
It's actually fairly trivial to write your own code to do this, especially since WP provides plenty of features for data integrity checking, sanitation, and security. There's a plugin here that does various data capture things: http://wordpress.org/extend/plugins/wp-email-capture/ that might work on your version but to be honest I've spent far more unhappy hours debugging and customising other peoples' plugins to do what I want than I have just writing something from scratch myself in the first place.
You may want to familiarise yourself with the WP plugin development section of the Codex: http://codex.wordpress.org/Writing_a_Plugin
Found the solution in the form of a plugin called TDO Mini Forms. It allows for creation of custom forms with a very fine control of things and lots of options.