I wanted to do the same thing so what I did was, to combine my forum feeds I'm using this site which was really easy
http://www.feedcombine.co.uk/ (there's probably others ex: yahoopipes but it looked confusing)
Then I used the RSS widget in wordpress. (there's a few better plugin rss widgets) The default update timer is 12 hours (i think) for wordpress, I added this to my Wordpress theme functions so it displays latest posts more quickly. Change 1800 to whatever you need.
PHP:
add_filter( 'wp_feed_cache_transient_lifetime', create_function( '$a', 'return 1800;' ) );