Helper functions and aliases for WordPress.
A full list of helpers can be found in the documentation for the plugin.
You can find documentation in the api for the plugin.
Either install this as a mu_plugin or drop into wp-content/plugins/invoke-helpers, then install as a normal plugin through the admin area.
The functions in this plugin are mostly wrappers or aliases to other functions in wordpress. The main idea is that instead of calling something like get_permalink or site_url('/some-uri/'), you can call url($post) or url('/some-uri/') and then the function figures out which URL you actually wanted.
There are also some nice snippets for limiting words, limiting characters, checking the template, rendering partials, and debugging/dumping variables.
Adding new functions is great. Be sure to include proper doc blocks for the functions so that the API documentator can figure out the information for the functions.