Event Rental Systems - The best business rental software available.

Event Professionals Alliance - FB forum filled with many great folks in the industry offering support and advice.

Electronic Money Company - ERS highly recommends EMC for your Payment Gateway needs

Fotoflexer - a free photo editor that is very simple to use. Great when you need to resize your images or make transparent backgrounds.

Logo Maker - a free and easy to use website for making logos.

GoDaddy - very easy to use registrar.

Constant
Contact - reasonably priced email marketing application that works well with ERS.

Mail Chimp - reasonably priced email marketing application that works well with ERS.

A Weber - reasonably priced email marketing application that works well with ERS.