If it's the moving of files between operating systems that you're finding interesting, you should have no problem mounting NTFS partitions in Ubuntu and just doing drag and drop (Ubuntu should have done it automagically I would have thought). You can also mount EXTx partitions in Windows but you'll need to buy some software, probably.
If it's virtual machines you want to play with, you could try VirtualBox within Ubuntu and install Windows within that. I cannot think of a single reason, other than "just for the hell of it" that a home user would want to mess with VirtualMachines unless you're a homebrew developer who wants to run emulators but develop in Linux.
Recent ubuntus seem to find ntfs file systems themselves -not so easy the other way round, as you say.
Vitualbox/ vmplayer -don't mind which. It's no longer some weird ultrageek/pro only thing 'though- anyone can do it.
Reason for doing it at home is same as dual boot- some applications can only run on one OS. Virtual machines let you use any application on the same machine without rebooting, and pick from a variety of software obtainable at the right price point (£0.00 ideally)
Example of home hobby use - I'm making a little gadget which needs a printed circuit board and machined lump of metal. The PCB is designed with a free layout tool (Designspark from RS components) on win7. The metalwork is designed with a 3D CAD tool(Alibre)which was a special deal ($99) a couple of yeas ago, but isn't supported and only runs on XP. Other useful things include a simple 2D drawing tool QCAD (free on linux, commercial on windows), a toolpath planning/code genrerator Cambam (free trial, may buy, windows only), various python scripts (any platform mostly). The software which drives my partly homebrew CNC milling machine (EMC2) is open source and only runs on linux- most conveniently ubuntu.
Hence, every tool in the chain can run seamlessly on single computer.
Ok this is a slighly industrial 'home user' , and draws partly on professional knowledge but no more so than some photography/music graphics etc enthusiasts. All home computer use beyond basic internet access, email and typing is pretty much just for the hell of it . We got along quite nicely with paper, stamps, and calulating machines before the 1980s. Nowadays there's a lot of fun to be had by anyone ( including the OP, I'd assumed) willing to think beyond fancy typwriter.
Oh - MichaelM - you're right - at least 1Gb / machine, real or virtual. memory's not that expensive, 'though.