Free content will not bring visitors to your website. However, another website's content can make the user experience better, so Luthernet is fine with using it. For example, if you don't plan on updating your website often, then embed your Facebook page. If you want some interesting added content, you can use a news scroller or verse-of-the-day module.
The main warning for using embedded content would be time and links. Your website loads a bit slower with embedded content, and the code always has an outbound link, so just be aware of that. Here's a basic iframe code that will work for most websites:
<iframe src="http://luthernet.org/your-new-site"width=100% height=2000
<p>Your browser does not support iframes.</p>
Just change the Luthernet link to your choice of website. Websites like Lutheranism101 or Feedgrabbr can provide you with code to paste onto your website--the feed posted on this page is from Feedgrabbr).
If embedding content isn't your thing, providing links to websites that update weekly is also a good idea. One such website is Lutheran Radio Church Service, which provides a half-hour WELS / LCMS church service WEEKLY. This means that if you put the link on your website, there's always new content on the linked website. If you can't put in the time to create a lot of your own content, at least choose a few linked websites that can help you look like you're keeping content fresh.