Luke Wroblewski wrote a nice overview article on responsive web design, with very practical links embedded (not just the ‘theory’ about how great it would be):
Media adaptation remains a big challenge for cross-device design. In particular, images, videos, data tables, fonts, and many other “widgets” need special care. Jason Grigsby has written up the situation with images and compiled many approaches for making images responsive. A number of solutions have also emerged for handling things like videos and data tables.