I have been through a bunch of Linux/Windows solutions including dual boot, VirtualPC, Parallels, and VirtualBox. I also tried Topologilinux, which I really liked. However, Topo is based on Slackware and doesn't stay up to date as much as I'd like so I eventually quit using it. Topo's claim to fame is that it uses CoLinux to run under Windows without full virtualization and also allows you to boot into the same Linux partition "for real" (that is, without Windows).
Recently I've been trying a similar setup called AndLinux (http://www.andlinux.org). It works great. Based on Ubuntu and CoLinux, it just seamlessly runs Linux apps along side Windows. Each Linux app just shows up on your desktop as though it were any other program. It doesn't, however, have a "for real" mode like Topo, but the performance is great (owing, I'm sure, to faster hardware and improvements in CoLinux).
The program is free and very easy to try. It can read Windows disks (even NTFS) and works great with common apps like Firefox, Thunderbird, and OpenOffice.
So far, this may be the best Linux/Windows answer I've tried to date. Out of the box it uses two network adapters, a TAP adapter for access to the local machine (fast for X) and a Slirp connection to the outside world (which is moderately slow). That means X from a laptop was very slow, but being familiar with CoLinux, it was easy enough to set the thing up to use a bridged TAP connector which is much faster.
Submit to: Del.icio.us | Digg | Slashdot | Diigo