A terrific and often under utilized function in WordPress is the fetch_feed() function. Basically it grabs an external feed and parses it using simplePie and feedCache, this is great as it means WordPress has built in functionality to retrieve, handle and cache.

Any website that displays an rss feed can be read, so you could display latest posts, news or even a twitter feed. Here is the Official WordPress documentation for fetch_feed()

I’ve used this function before for a particularly complicated sitemap that was part of the same domain but using a different CMS, using it to display a twitter feed is the obvious possibility for me, but you can literally use it for any feed.

The only tricky part is altering the cache of the results, the code below is used in your functions file to alter the cache transient lifetime (in seconds)

add_filter( 'wp_feed_cache_transient_lifetime',
             create_function('$a', 'return 1800;') );