Webcomics:
http://www.diggercomic.com/ Digger
http://dresdencodak.com/ Dresden Codak (probably my favorite webcomic); has flavors of transhumanism, is typically relatively intellectual
http://drmcninja.com/ Dr. McNinja; it's exactly what it says in the title: a ninja who is also a doctor; start from the beginning of the series, it get's incredibly awesome while still somehow not getting too silly
http://www.smbc-comics.com/archive/ SMBC; daily comic (over 2000 in archive), usually really good and often applicable to real life... sort of like what political cartoons would be if they weren't steaming piles of shit
http://www.picturesforsadchildren.com/index.php Pictures for Sad Children: something of a surreal webcomic about life
http://www.rice-boy.com/ Several webcomics by the same author; Vattu is the current one in progress; all pretty good with a somewhat abstract art style.
http://www.lfgcomic.com/page/1 LFG; starts out a bit of a typical MMORPG'ish based webcomic, turns into more of a fantasy epic
Podcasts:
http://radio.seti.org/episodes Big Picture Science, previously called Are We Alone; done by SETI folks, general science podcast (though rather corny)
The next few podcasts are Skeptic podcasts; they're generally worth listening to if you have time. They cover all sorts of things people get taken in by; things ranging from common myths to conspiracy theories as well as just general science.
http://www.theskepticsguide.org/archive/podcast.aspx The Skeptic's Guide to the Universe; hour long weekly podcast covering several topics each week; over 300 of them dating back to '05.
http://www.yrad.com/cs/ Conspiracy Skeptic; hour or so long podcast, typically with an interview style, with a conspiracy theory discussed each episode, everything from Truthers and Reptoids to The Homosexual Agenda.
http://www.skepticality.com/ Skepticality; another about an hour long podcast, typically with an interview style and about one topic or a small range of them
http://monstertalk.skeptic.com/ Monster Talk; podcast about various mythological creatures and generally things which would fall under the 'monster' category; things like Nessy, ghosts, ect
http://skeptoid.com/ Skeptoid; weekly podcast with a relatively short format, typically about 15 minutes or less, usually discussing a particular topic; there are about 275 of these on just about everything
I could keep listing more, but if you simply google 'skeptic podcast,' you can typically find quite a few good ones. Most have pretty good discussions, but quite a few also have bad audio quality, especially if you go too far back in their archives. But on the plus side, there are simply so many you can continuously listen for weeks before running through the archives of all the ones you like.
Other stuff:
http://www.popsci.com/ Popular Science; updated with science and tech news several times daily (except weekends), very up to date, usually covers science info on the same day it becomes available, making it a good place if you only want to check a single website (you can of course get news several hours faster from more specialized single-subject websites).
http://www.rockpapershotgun.com/ Rock Paper Shotgun; PC Gaming news site with pretty good analyses
As for getting around the character limit, it should be sorted by topic, with each topic given it's own post, with links to those posts in the original post. Ideally you should grab an entire page or two of consecutive posts and reserve them for when they are needed (to allow for scrolling through the posts w/o going back and clicking links to each subsection).