Toxic Software's posted a useful little script if you spend any amount of time in Xcode-- because manopen is having trouble with Leopard, John punched up a shell/Applescript to open man pages directly from within Xcode's command line. It's tiny (and doesn't really do much-- just opens an Xcode Help menu item), but it seems useful-- straight from the command line, you can break out the man page within a GUI, and just keep right on coding.
Because the script uses UI scripting, you've got to enable an option in Universal Access preferences, but then just toss the script in your PATH and you're good to go. I can't imagine it's hugely relevant for everyone out there (I haven't put anything together from the command line in Xcode in a while), but anyone building stuff there will probably appreciate it.
And if viewing pretty man pages from the command line is your thing, Atomicbird Software came up with a script that breaks out man pages in PDF form. If you love working from the command line but love reading man pages in something a little easier to browse, today's your lucky day.