Do you have a newsletter that you always read as soon as you see it in the inbox?
I love the Threadless newsletter, and I always read it straight away, partly because the shirts it promotes each week are only available in limited numbers (especially if you are Mr Average Size like me).
I also like the Itunes weekly email that tells me which music is out or newly added to Itunes. Recently I've also realised I subscribe to a few newsletters that I never actually read, and I'm starting to unsubscribe from them. What about you?
I love my daily surf reports from AquaBumps. Bondi doesn't typically have the best waves but the photos are always amazing.
On the tech side of things, the Simple Talk newsletter always has plenty of good content, and Good Morning Silicon Valley gives a good overview of current news in the industry (and is usually pretty funny).
And finally, the Elsewares newsletter comes through about once a month with some very fun and unique products.
Laura Carlson's Web Design Update is very good; I've been getting it for years now and always end up with a dozen open tabs after I've read it.
It's ugly as sin, but I always scan promo emails from Harbor Freight Tools -- I'm remodeling my house and always looking for good bargains. (They have a store a couple of miles from my house.)
I get one of the Sitepoint newsletters (I can't remember which one!) and it's got a great voice and good links. Plus when I got the text version I was always impressed with the quality of design.
I subscribe to around 30 newsletters just to see what others are doing in the way of design and trends....my recent favorites are from http://www.bbcgoodfood.com, the design is really gorgeous great use of color! and they have great food photos and recipes.
http://www.fontshop.com have an email called fontshop news...again a nice clean layout.
I also like Men's style from GQ http://men.style.com/gq it always has links to good articles and interviews..I originally subscribed for "research" but found I like reading the interviews and looking at men's fashion articles which I get ideas from for our menswear clients.
I love Threadless's newsletter -- best combination of content and design.
The Onion's newsletter has great content and passible design, but it doesn't fare well on mobile devices.
And I read Variety and Hollywood Reporter's daily newsletters for their content, but they're horribly, horribly ugly.