neocomplcache (GitHub: Shougo / neocomplcache, License: MIT) by Shougo Matsushita is a keyword completion plugin. It supports configurable completion for quick matching, snippets, filenames, and registers. It also enhances omni completion, and works with VimShell.
The author's readme on GitHub has configuration examples and screenshots of each feature.
fisa-vim-config (License: GPL) is Juan Pedro Fisanotti's
.vimrc that's focused on Python development and uses Vundle for managing plugins. It includes smart completion, a fuzzy file finder, class and module browsing -- basically everything to turn Vim into a Python-friendly IDE.
Juan has included documentation that explains the keyboard shortcuts and installation details using Vundle. There's also a link to each of the bundled scripts.