I will also mention the WODE people and a few others have announced optical drive emulators that can read from USB. They are not out yet and do not afford half the niceties of a JTAG 360 not to mention are set to have a fairly hefty price tag but I suppose it does fulfil your "USB loading of games" thing you seem to have got yourself set on doing.
Back on topic as it were.
First you would need a JTAG 360.
If you buy one most come with it and if you follow one of the guides you will usually end up with it but after that you need a hacked dashboard- technically speaking it is not hacked though but a small dash reboots into a hacked one (this gives us the term rebooter) that patches out many of the blocks (others are left to a program called dashlaunch). Originally there were two but nowadays "fbbuild" (named for an older hacked dash that spawned this called freeboot) is the only one to see updates.
You say you know wii hacking so I will try and explain it in terms of things you might see there but once the rebooter is done there are many ways to run code but the big three are
Freestyledash (usually abbreviated FSD)- this is akin to one of the full blown loaders with covers and all that jazz. These days some nice options with regards to title updates (games get updates and these are how they tend to come) and VPN management are getting added.
Originally there were a few competing dashes on the fancy loader front with the most notable being 360 dashit (it mainly being noted for better XBLA support from USB) but this is the one that emerged "victorious".
Xexmenu- this is perhaps more like the homebrew channel or Neogamma. Small, mainly text based, quick and lacking some of the niceties of FSD but it loads quick and runs games very well.
Some form of jump loader (quickboot
http://www.xbins.org/nfo.php?file=xboxnfo1773.nfo is the most common). This is akin to a forwarder channel but few use them nowadays as the other methods are easier in the long run.
Some homebrew installs and appears as an XBLA title might- the chicken and egg problem is avoided by the DVD drive, a USB drive "formatted" to 360 standards and injected using something like xtaf with a loader, a 360 drive or memory card accessed by external means and some got creative with dashlaunch*.
I should also reiterate that many do not go in for USB loaded stuff- with a JTAG 360 you can stick any size sata drive (laptop mainly unless you want to power a full size one) and with that you can load XBLA, DLC and GOD installs (when you download a full game from Live you get one of these, NXE "install to hard drive" type installs are but a few bytes different from a GOD install so there are even programs to convert ones already on the hard drive). Of course the hard drive is regular storage too so you can use it similar to how you might use a USB drive.
DLC needs a hard drive, XBLA can be run from USB but using a hard drive is easier and I am not sure where GOD installs from USB are at but if you are running from USB you have the other methods anyway. At some points GOD installs solved problems with USB loading but that is very rare (indeed I am struggling to think of anything other than fable 3 and maybe some of the region checks) and at others they fell short (mainly the rise of AP2.5).
*I mentioned it a few times in here so I might as well cover it- dashlaunch is perhaps akin to preloader/priiloader/starfall/startpatch on the wii but with the main difference being it can load a patch for the dashboard giving you a choice or sparing you having to install it to the NAND (much like most hacks the less you can write to the NAND the better). Patches are usually made for this program although they tend to get merged into dashlaunch or the main hacked dash as time goes on.
The original use of it was to give you the option to load some homebrew instead of the original dash (which is pretty poor on the homebrew options front for obvious reasons) and many use it to load their chosen homebrew/game launcher.
Equally if you are coming from the Wii I should note that USB drive model/version and the like does not really matter. I am hesitant to call it PC grade but you will usually have to go searching to find yourself with a USB adapter that does not work.