If the font is large enough, serif fonts are not an issue even on screen.
The predominant problem of serif fonts on screen is the rendering accurate of the tiny serifs without creating visual clutter. But with modern displays, modern font rendering techniques (ClearType anti-aliasing and proper hinting) and large fonts, this is not an issue any more.
The advice of using sans-serif fonts in favour of serif fonts is therefore outdated, and using serif fonts on screen has the same advantage that it has in print; namely,
[…] that serifs help guide the eye along the lines in large blocks of text. [Source]
The only potential problem is that not all fonts were designed with screens in mind, and are therefore poorly adapted to ClearType rendering. A properly hinted font mitigates this.
Next-generation displays (Apple’s Retina Display) promise to make even that obsolete: their resolution is so high that the naked eye cannot distinguish individual pixels, and text looks as smooth as in high-quality print1.
For now, though, most displays in use still have comparably low resolutions and require properly hinted fonts for best rendering. So, in summary (for now): Use a large font that was designed for on-screen usage. Serif or sans serif is irrelvant.
For inspiration, look at the free fonts listed at the Google Web Fonts directory, especially Vollkorn or the Droid Serif font which was particularly developed with small font size in mind.
1 Ironically, the article does pretty much the opposite: it uses a small font which, though developed for on-screen usage, contains hinting errors and looks smudged: