The proposed change to our current sound laws include lowering the legal decibel level for how loud music can be at venues and music gatherings. This also includes not giving sound permits to venues located within 100 feet of a residential zone.

This is incredibly likely to affect your bar, your band, etc. Understand that this is where it starts. This is the move that will sooner or later will have a dramatic effect on Austin's independent music culture.
Resources (courtesy of Philippe LaVere's blog)

The City's announcement of the Town Hall Meeting:
http://www.ci.austin.tx.us/news/2007/music_town_hall.htm
The Noise Solutions Committee report:
http://alt.coxnewsweb.com/statesman/pdf/10/101807noise_report.pdf
Downtown Austin Emerging Projects:
http://www.ci.austin.tx.us/downtown/downloads/ep_data_0707.pdf

So you ask yourself, "What can I do to help?"
-- Write a respectful letter to City of Austin leaders including Mayor Will Wynn, The City Council, City Manager Toby Futrell, The Austin Music Commission, and Austin Police Dept.
-- Attend any town hall meetings or public forums held to discuss the proposed sound ordinance change (or upcoming changes)
-- Make signs or bumber stickers for "Keep Austin Loud" and share with friends.
-- If you're in a band, dedicate a small section of your flyer for a KeepAustinLoud logo or remind people to KeepAustinLoud in your mailing list emails or bulletin posts.
-- Place the KeepAustinLoud badge on your MySpace/Facebook pages.
-- Become a KeepAustinLoud venue or retailer by placing a logo on your door or in window.
-- Write letters to our local newspapers, radio stations, webzines, and TV news outlets requesting continued support from our local media.
-- Go to shows, support local bands, buy music and goods from local stores, and keep on keeping the Indie spirit of the Austin music scene rockin.