I've whipped up a very simple script that outputs the names of users in a specified forum. However, I can't figure out how to pass this info on so that it's parsed as a variable in the forumhome template. Any help would be greatly appreciated.

as long as the variable has a value before you evalute a template containing the variable it shoud work.

$test="This is a test";

eval("\$stuff = \"".gettemplate('some_template')."\";");
eval("dooutput(\"".gettemplate('another_template') ."\");");

You need to make sure that the variable is declared and has a value before evaluating the template with the variable within it.