I'm pretty picky when it comes to newsletters in my in-box. If they don't have the ./ mantra of 'more signal, less noise' then I'm frankly not interested.
If you are interested in what is going on in the world of Life Science then Genomeweb is a must. They will rent out the email list on occasion, but it is still a very worthwhile read. There are print editions of their bi-weekly newsletters, such as BioCommerce Week or BioArray News, but you have to be prepared to shell out a few hundred $/year.
Another newsletter I subscribe to is the Biospace Genepool, if only for the jobs that are posted there. They do put on local career-hunting events, which may be of interest should you be in the market for a new employer.
A pretty short list - only two newsletters - and there are many others you can subscribe to that are whittled-down versions of trade publications, such as The Scientist, and for a while I subscribed to Nature and Science Alerts which can be useful if you want their Table of Contents delivered weekly.
General marketing newsletters I subscribe to are 'Go-to-Market Strategies' Resource newsletter, the McKinsey Quarterly newsletter (free content articles are available) and stuff from Perry Marshall regarding advertising via Google Adwords.
A hint about newsletters: simply set-up a free email account such as Gmail by finding an 'unused' invitation in this thread. (With over 70 pages of invitations, at least one of them should be still valid!) That way all your newsletters are in one place, and any commercial email will go to that address keeping your inbox clean and tidy.
Hint number 2: Reserve your own domain. I use this service for something like $10/year. (For example, www.lastname.com, if not taken already.) Then you can setup a personal webspace via a web hosting service (I use this one, only $30/year) and have it auto-forward everything sent to [email protected] to [email protected]. This way if and when you move or your ISP goes out of business or you switch from AOL to DSL to another DSL and then to cable (or whatever), your email address stays blissfully the same. Of course you have to keep track of two email accounts, the personal one you guard jealously and the one you give out for commercial purposes, but once you set it all up life is good!