Most Elgg site Admins search for OpenX  Elgg Widget or plugin that  provides a simple, straightforward way to place ads from an OpenX AdServer.

Here are five good links for anyone searching for how to add banners to Elgg site and monitize Elgg site:

1. Elgg ads or banners plugin for elgg
2. Elgg and openx online advertising adwords adsense and banner ads integration plugin
3. How do i make adsense program worked on my elgg site
4. Adverts and ads and boost traffic on Elgg websites
5. Advertising banners etc... to elgg

Comments and suggestions are welcomed.

Hope it helps someone.