Here is a more detailed Listen check DC list. It is based on decibels and ranges.
Game Rules 
Custom Rules
Custom Rules
This article presents alternate rules for Purchase Difficulty Class (PDC) to cash-value conversions and for comparing Wealth bonuses to lifestyles.
How to nail someone to a wall by their clothes.
Zero-G presents a unique set of challenges for the d20 Modern rules.
Rules for swinging from a rope in combat or as movement.
Knockback rules built for specifically for a super-powered universe.
One of the recurring issues with any roleplaying game that involves a lot of action is how to balance events that happen near-simultaneously while maintaining a turn-based system that promotes a shared understanding of action sequence and player engagement. One of the systems that I have previously played that does this perfectly is Car Wars. Using their concepts for turn order and speed, I've come up with some new rules for driving rules that only apply at chase scale.
Phoenix is a superhero expansion manual for d20 Modern. It includes new classes, altered feats, a crappe-tonne of super powers, and specialised rules for running magic, technology, and superpowers all in one game as well as a load of optional rules and a chapter full of sample heroes and villains.
Download Phoenix Beta 10 Ultimate (2.24 MB 2010-10-20)
Download Phoenix Beta 10 Ultimate (2.24 MB 2010-10-20)
These tweaks to the Wealth system plug a couple of its loopholes and offer a few extra options (Relative PDCs, Handling Cash, Wealth Pools).
A quicker resolution to iterative attacks.
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Favorite Custom Rules
by Tahsin Shamma, 5 with 5 votes
by Orion, 5 with 4 votes
by Orion, 5 with 3 votes
by Tahsin Shamma, 5 with 2 votes
by Orion, 5 with 2 votes
by Orion, 5 with 2 votes
by Tahsin Shamma, 5 with 1 vote
by Don Sauber, 4.8 with 5 votes
by Tahsin Shamma, 4.75 with 4 votes
by Orion, 4.67 with 3 votes