If you're anything like me, for a graphics designer you make a great web developer.
My past attempts at design have run the gamut from "geocities" to "unicorn vomit", and I've become increasingly minimalist in an attempt to rectify that
-> less design == less unicorn-puke == win!
But it still leaves my sites looking like crayon-drawn whitesites
It's a long way from there to the current industry requirements of a clean, flexible, responsive design - able to handle mega-huge desktop-monitors and tiny smart-phones alike while looking sleek and professional... and I had resigned myself to basically just not sucking too badly and hoping my sites were useful enough for people to get past the ugly-duckling look.
but now I've found bootstrap. It lets you quickly and easily build a fully-responsive all-devices-ready design with very little graphic-design nous required. From a full grid-based system (to easily build columns that will nicely collapse on smaller screens), to all sorts of components - navbars, breadcrumbs, panels, lists of linked thumbnail images... the list is pretty huge.
Don't be put off by the "oh my god PURPLE" look of their website - this is a tool worth using.
The getting started guide is where to begin.
There's a number of pre-built templates on bootply templates that even if you don't like, you can cannibalise for the various pieces you want.
You can also buy a whole bunch of pre-packaged, professional themes (for about $12 each) from WrapBootstrap to kickstart your website design. Though be aware they are mostly built on Bootstrap 2
If you're building this stuff in rails, there's a whole bunch of bootsrap-related gems - which mean you don't have to download the css/js versions of bootstrap and mix them all into your assets directory.
Ryan Bates' railscast (see below) uses seyhunak / twitter-bootstrap-rails, which seems to have a whole bunch of neat generators for quickly throwing up layouts. I prefer not mixing bootstrap's Less with the existing SASS, and so have gone for the sass-based gem: bootstrap-sass gem.
I suspect you can combine these two powers for good by using the generators of twitter-bootstrap with the sass-based assets of bootstrap-sass... but have yet to try it (let me know if you do).
There's also a great overview of rails and twitter bootstrap with a related RailsApp that goes into far more depth (I haven't had a look at that yet).
Note: Bootstrap version 3 has recently been released, and a lot of the tutorials, railscasts etc are based on version 2. Bootply has a Bootstrap 3 migration guide if you want a reference to what has changed.