Thanks for the responses. Here's a couple of build pics (again - apologies for the rubbish quality, I'll got some better ones for the weekend)
I'm using a minipac to drive the joysticks, buttons and U-trak (all from Ultimarc) and the turbotwist (Groovy Game Gear) has its own encoder - all plugged into USB
The PC is an Athlon 64 3.2Ghz with 2gb ram, a 200GB hard disk and a Geforce 5 graphics card.
The T-moulding is orange 3/4" from t-molding.com and finally, the over/under coin door came from Gremlin Solutions.
I'm trying not to think too much about how much it all cost :-)
The marquee I designed in photoshop using Arcade-Art to get the Space Invader side-art monster (thanks to Zorg et al for creating the excellent illustrator file). It was very kindly printed by a guy at my work.
I designed the whole cabinet from scratch in a 3D program called AC3D at the start of the project and that really helped me work out all the niggly little bits (like monitor mounting etc) in advance so when it came to the build I didnt have to make too many adjustments.
The frontend is Mamewah, which is fantastic for this, and the usual other emulators - MAME, Nebula, Fusion (genesis) and zsnes - I've still got to setup the PSX, N64 emulators and set up some good cab friendly PC games on there like Trackmania, Geometry wars etc.
If you have any specific questions pls post!