Ghostscript is a PostScript interpreter freely available to end-users, written by Peter Deutsch. It can read the PostScript produced by Dvips and render it on your monitor, or for another device (e.g., an Epson printer) that does not support PostScript, or in PDF format. The latest version is available via @url{http://www.cs.wisc.edu/~ghost/index.html} and @url{ftp://ftp.cs.wisc.edu/pub/ghost/aladdin/}.
A somewhat older version of Ghostscript is available under the GNU General Public License, free to everyone. You can get that from @url{ftp://prep.ai.mit.edu/pub/gnu/}.
The program Ghostview, written by Tim Theisen, provides typical previewing capabilities (next page/previous page, magnification, etc.). It requires Ghostscript to run, and files in structured Postscript, specifically with `%%Page' comments (no `N' in `config.ps'). You can get Ghostview from the same places as Ghostscript.