I once worked for SLM Electronics, manufacturer of Crate Guitar amplifiers and Ampeg bass amplifiers. The place was very casual--some had long hair, some beards, some wore shorts or jeans. Very laid back.
In the U.S. there used to be a very distinct east coast vs. west coast difference in office attire, but I'm not so sure that's still as true as it used to be.
Here in the desert, standard engineering attire is jeans and either a button-down shirt or a polo shirt. Some people wear shorts and sandals in the summertime, but they are in the minority -- although I don't get any sense that it's frowned upon.
Managers tend to dress a bit nicer than engineers, at least as far as replacing jeans with Dockers or dress slacks (sometimes). No ties, ever! That reminds me, we have a few bars around town -- of the cowboy variety -- where if you walk in wearing a tie, they will cut it off with a scissors and hang it on the wall of shame :)
Here at Freescale, Friday has been Hawaiian shirt day for as long as I can remember, but participation waxes and wanes throughout the year.
And if you come in on the weekend, you wear your Iron Maiden t-shirt or whatever your favorite rock & roll t-shirt happens to be :)
I usually wear jeans or casual pants and a long sleeve oxford shirt or polo shirt in the summer. In the winter I often wear a nice flannel shirt and corduroy pants. I also usually wear leather hiking/work boots. I also am usually seen wearing a zip-up hooded sweatshirt to keep warm enough in the AC...
Long pants and button-up shirts (or polos in the summer) are the norm here. The guys who want to move up into management wear ties....
This thread does bring up the question that I've been wondering about. What is the female equivalent of a tie? I think its a good thing that as a female engineer, I'm not required to have any fashion sense.