I find the focus on building portfolios frustrating. Mostly what I've seen it accomplish is people writing dumb scripts that don't do anything particularly useful or basic web apps that would never be useful for anything beyond the toy case the author came up with. That's not to knock building small programs like these to develop skills or become familiar with a new library, but it's hardly an adequate way of showing…
My GitHub account contains a mix of (a) small pieces of functional software used in niches that are poorly supported, such as non-delivery report processing in Drupal, (b) dumb things that were amusing enough to write, such as a self-propagating bash script, and (c) functional examples for software that lacks good functional examples, such as the use of Guice in DropWizard.
This sort of thing seems more than good enough to demonstrate that you know what you're doing.