You may not be aware, but there are a set of fonts that were developed for a Microsoft project that intended to produce a pack of core fonts for the Internet (see this Wikipedia article for more information).
If you're a Windows or a Mac user, you'll already have the relevant fonts installed as part of the base operating system, however, Linux users aren't so lucky. De to possible license issues, the core fonts aren't generally included as part of most distributions; I've had to install them myself on my desktop running CentOS, and my two laptops, one running Fedora 7, the other Fedora 8.
Now, when I first started using Linux, I never ran into any font issues, so it was only fairly recently that I found out about these "core fonts" - you are probably wondering why you need them on a Linux system. Well, there are two reasons for me installing them on my machines:
To install the core fonts on a Red-Hat based system, simply follow the instructions on the core fonts Sourceforge project page. This method packages the fonts into an rpm file, which you can install with your package manager of choice.
For Debian based systems, there's a pre-built package available in the contrib repository - there's a guide to installing the fonts, as well as Flash over at the . For Ubuntu, the package is available in the multiverse repository.