I went through a series of panels before settling on fbpanel, the one I use now. All of these are great panels, and I still have them installed, but fbpanel just has everything I want on it.
xfce4-panel is the most user-friendly of the ones I’ve used. It has all the basis requirements, and plenty of extra plugins for extra functionality. It’s got the basic menu button, launcher, taskbar, pager, tray, and clock, all of which can move around on the panel. The plugins allow all kinds of fun things. When I was using xfce4 regularly, this was (obviously) my panel. Like everything else about xfce, it’s lighweight but very functional. Of the ones I’ve used, it’s the only one configurable directly from the panel itself, not a configuration file, with its drag-and-drop launchers and GUI configuration. At some point, though, I switched to using window managers and tacking on the other pieces of the desktop myself, so I stopped using the integrated desktop environment system.
Tint2 comes with both ArchBang and CrunchBang. For good reason, too. It’s incredibly lightweight, and easily configured from its ~/.config/tint2/tint2rc file. However, that lightness comes with a few pieces missing from what you might expect from a standard panel. It comes with a taskbar, tray, battery manager, and clock. The rounded-ness, color, and size of the panel is customizable. It does not automatically come with a menu, a launcher, or a pager. Don’t fret, though! The svn version in the AUR has launcher functionality from linking to .desktop files in /usr/share/applications, though the buttons don’t “click,” they’re merely icons pasted on the bar. There’s a way to hack an openbox menu onto the launcher by xdotool-ing openbox to open the menu when you click on an icon, but it’s not the prettiest. And neap, also in the AUR, adds a pager to the tray; there are also several other pagers there that don’t sit inside the panel directly, but still work well.
Bmpanel2 is kind of interesting. It doesn’t have config files like tint2 and fbpanel, relying on sets of themes, which are quite nice to start. The themes are easily and highly configurable, if not quite as accessible as the ~/.config/ files. It comes with a pager, a launchbar, a taskbar, a tray, and a clock; they remain in that order and can’t be swapped around. The launcher (which has “clicking”!) requires a command an an icon location.
Finally, fbpanel. It comes with the usual (and reorderable!) components: menu, launchbar, taskbar, pager, tray, clock. It also includes several monitors, like for cpu and memory, but I’m using Conky so I don’t use them; also, for some reason, my volume doesn’t work, but I use volumeicon or pnmixer for that, so it doesn’t matter either. It’s configured through files in ~/.config/. Unlike tint2 and bmpanel2, it uses your GTK theme and icons (clickable) and such, so if you like a unified desktop, it makes it easy to do so. You merely need to change the background color. It also allows for transparency, though whether that’s fake or true I’m not quite sure.