Minimizing scripts & css files that plugins add

I would suggest using a minify plugin that will automatically combine all the scripts and styles for you. Here are a few that will do it for you:

http://wordpress.org/extend/plugins/w3-total-cache/
http://wordpress.org/extend/plugins/bwp-minify/
http://wordpress.org/extend/plugins/wp-minify/
http://wordpress.org/extend/plugins/minify/