There are formal emergency nets such as skywarn, and ARES/RACES which handles disasters of all sorts. There are traffic nets, dedicated to passing written messages ("traffic") between hams and non-hams, coordinated as the National Traffic System (NTS) which operates under methods and practices developed over the years by ARRL. Finally, there are informal social nets of all sorts.
ARRL: search for a net
|Orange||70cm, announced (above)||thursday after 2m net|
|Seminole||147.285 / 147.165||most days, 7:15pm|
|146.820 146.760 443.275||Sunday 8pm||scanning/listening||Central Florida Listeners Group|
|147.060||Sat 8pm||rag-chew net||Central Florida Repeater Association|
|146.76 / 443.275||Monday 8pm||Traders Net||OARC|
|146.76||Thursday 8pm||Ladies' Net||OARC|
I've done my best to find a list of all nets within my listening range. I've I've left out your favorite net, feel free to drop me a line and I'll add it.