As far as sources, especially starting out I liked -
Jeffrey Zeldman’s Designing with Web Standards as a great place to start for HTML and CSS, gives you some basics of the how, but also a lot of the why that you won’t get in most manuals.
Bulletproof Web Design again gives you a lot of CSS and HTML and shows you how to make your sites less fragile to changes and situations you may not be thinking of right then
For PHP I’ve loaned out my copy of the SitePoint PHP book (Build Your Own Database Driven Website Using PHP & MySQL) so many times and everyone picks it up really easy from there. I know they’ve released a couple updated versions and you can find them at <a href="sitepoint.com">SitePoint</a> which is also a good reference for articles on fairly new technologies as they become available. Their forums have a lot of good people who don’t mind sharing what they know as well.
As far as web design, I like checking out <a href="smashingmagazine.com">Smashing Magazine</a> and <a href="stylegala.com">Stylegala</a> for inspiration on the pretty stuff. <a href="dzineblog.com">Dzineblog</a> is newer but has some interesting gatherings of design in general.
You asked which is preferred for daily use, I generally use books and magazines to learn new skills and ways of thinking while using the online tools as quick references and great places to look for browser rendering quirks and things like that.
This is becoming pretty long so I’ll let you go with one last thing. The most worthwhile reference I’ve been able to find is always finding a local web design group wherever I am. Books and websites are great but having someone explain something face to face or give you feedback right away on a design always seems much more motivating to me. If you’re in the US, I’ve had real good luck with the Refresh groups (refreshcities.org) but there seem to be similar communities just about everywhere.
Good luck with it and have fun,