This is where I'm trying to get some advice from you ;-)
Each newsletter is focused on a topic or natural collection of topics. What source is more focused on, say, Ruby than Ruby Weekly? I would find this useful advice! :)
Or are you saying you'd rather see, say, 3 or 4 links a week related to a topic.. and it's a problem with the volume rather than subject "focus"?
I am the author of "Practicing Ruby" ( http://practicingruby.com ). It's a paid newsletter but I offer it for free for anyone who can't pay for it, and try to release back issues relatively frequently.
I'll plug mine as well: Hacker Newsletter - http://www.hackernewsletter.com, which is a product of what I said above. :)