The new version of XFCE, known quite creatively as xfce4 (4.4 being the most recent release), is similar in look and feel to the earlier version. However, it includes numerous other features which make it far more flexible and customizable than earlier releases.
Among XFCE4's most notable features include two different panel-menu applets which provide Start-menu styled menus. The first one provides a menu in the style of that seen in KDE or Windows NT 4.0, with the same contents as the right-click desktop menu (which makes its triumphant return). The other panel-menu applet provides a Windows XP-type menu, though this is pretty beta and a major pain to set up for now (Even the Debian, Gentoo and Solaris-Blastwave packages don't get this right). Expect the XP-oid menu to be better in the future, but for now the classic style menu is the preferred one. The stock panel doesn't have either menu applet, but it can be added with just a few mouse clicks. Also new in XFCE4 are panel-based monitoring applets, a mini command line, numerous clocks and both graphical and CDE-style desktop switchers. Other panel plugins have been written by third parties.
As of version 4.4, XFCE ships with a new file manager, called Thunar. Thunar's look and feel is quite similar to Nautilus, with an icon-based view or list view, and a left-hand pane holding 'favorites', somewhat akin to NeXTSTEP's shelf. XFCE also integrates well with other file managers like ROX, XFE or Nautilus. It works passably, though somewhat less well, with Konqueror. As far as integration goes, XFCE is based on the GTK2 toolkit and as such integrates well with GTK2 (and GNOME) applications. Its 'default' web browser is usually Firefox, though Opera, Epiphany, Mozilla SeaMonkey, Konqueror, Galeon or even Elinks could be used instead.
It comes in at least five pre-packaged forms that I know of: The XFLD (XFce Live Desktop) distribution for Debian Linux (grade: A), the Xubuntu Linux distribution (A+), the Gentoo ebuilds for Gentoo Linux (A-), the Blastwave packages for Solaris (B+) and the graphical installers from OS-Cillation (B+). Of course, the source code and some RPMs are available from xfce.org, too.
If you use Debian (Sarge, Etch or Sid), installing it is as easy as adding the XFLD repositories to your sources.list (check out OS-Cillation for info on how), then running 'apt-get update; apt-get -y install xfld-desktop'. It should now be available as a session choice from GDM. Log in and enjoy!
On Gentoo, you need only 'emerge xfce4'. That's it. It takes longer, as it has to build everything from source, but the result is usually pretty quick.
On Solaris 8, 9 or 10, add the pkg-get tool from Blastwave, then do 'pkg-get install xfce4'. This should also add XFCE as a session choice in DTlogin, though if you toss that barfucious piece of slow, ugly junk in favor of GDM or KDM, you'll have to add the session manually.
On other platforms, try the graphical installers. These extract themselves, then build the installer from source (!) and run it, walking the user through the process of building XFCE from source. They actually make the process easy enough for newbies, unless something goes wrong. These installers work fine on Red Hat Linux, Solaris 10, FreeBSD 6.x and NetBSD 2.x and 3.x, though it takes some demon-wrestling to work right on OpenBSD. I haven't tried it on other platforms such as Mac OS X, AIX, Solaris 2.6 or IRIX, but theoretically these installers ought to work anywhere you can build XFCE from source.
There are official Debian packages for XFCE, too. The ones for Stable and Testing are for XFCE 4.0, however. The packages for Unstable are 4.2, but include fewer extras than XFLD. Just apt-get install xfce4 without adding the XFLD repositories if you want these. They /do/ have the advantage of being official, which means better supported. There are SuSE packages for XFCE as well, however, I was forced to build it from source in order to get version 4.4