Alwyn has a very good newsletter. I've been getting it for about 3 years.
He has some cool offers in there also (he just gave a free bodyweight training DVD and free shipping with his program design manual) that you don't hear about anywhere else. It's just a bonus for subscribers. Kicks ass.
What I really like, is alongside a Q&A Alwyn often interviews some other coaches and trainers (guys you may not have heard of). Good stuff and it never appears anywhere else.
A lot of guys have newsletters but it's just links to their website or reprinted articles. I hate giving my email address out so they are never worth it. The best ones have unique content.
Elitefts.com also has a really good one that you can ONLY get via email. They just sent one out today that had a killer roundtable discussion with all their team on supplements.
Joe DeFranco has another solid one, although you don't need to sing up - he prints it on his website.
Eric and Mike have just started doing newsletters too - but again, they put them up on their site too so you probably don't need to sign up - just check their websites regularly.
Anyone else have any good ones that I missed?