WTB: My first Amiga

[kvasir]

Yeah, the 1200 is definately a good choice. Relativly cheap for a basic unit, can use the same hard drive that can be gutted out of most dead laptops (Like the IBM Thinkpad I got sick of and ran over with a lawnmower. Ripped the HDD out first...), and the PCMCIA port can use ethernet/wireless cards. (16-bit only, but still better than dial-up. Though most DSL services are just starting get get WAN access that fast out where I am).
Granted most, if not all, of this has already been mentioned, as well as Amibay and Ebay, Craigslist sometimes has Amigas as well. I was lucky enough to find one for free, that some guy didn't want to throw away and felt someone might still enjoy. (That sort of thing is usually around spring-cleaning, and most of the time involves a spouse who is sick of old electronics cluttering up the place. Probably me in a year or 2) Also, Amigakit has been really good to me when I've needed stuff I could never find stateside. Though if anything you get needs drivers from a floppy, you might want to as for an ADF image e-mailed too. Customs seems to have hired some idiots that don't know what "Do not x-ray" means....
Anyway, good luck getting ahold of a miggy, it'll be worth whatever effort is needed!

[kvasir]

The 500 has at least composite output, and I believe it has RF modulated output as well. So even without a monitor, you can hook it to a TV (either through the aux/game inputs or straight into the cable jack, with an RCA->Coaxial adapter), but the quality won't be the greatest. Plus, unless you have a TV that can switch between PAL and NTSC modes, alot of software won't run right (running PAL stuff in NTSC can cause everything from timing problems and the bottom part of the screen getting chopped, to outright crashes). I think some newer LCD TV's might do both, though.
The mouse might be an issue, all the Amiga ones are ball-based (the only optical Amiga mouse that I used is the Boing mouse, though there were a few others as well, just none made by Commodore that I can recall), and get hard to move after awhile. Granted, I've always had cats/dogs/birds/etc..., which tend to jam ball-based mice quickly. But for the mice, a ps/2 or usb adapter would probably work great (on any model of amiga, not just the 500. My 1200 uses a USB wireless mouse via a usb -> ps2 adapter, and usb -> amiga adapter), and allow any $10 special from Walmart to work (possibly with a usb -> ps2 adapter as well).
There's no HDD interface, but there are some side-car adapters that have SCSI interfaces. The A501 TomJ was talking about hooks into the trapdoor slot, should give a bit of a speed boost if its FAST ram, not sure if expanding CHIP ram is even possible via the trap door. Plus the real-time clock is on it, though you might want to check the battery. (I think there's an Agnus replacement for more CHIP ram, but requires swapping chips off the mobo) If you dig up an A500 accelerator card that doesn't cost more than selling a kidney, it would use that port.
Also, its an OCS (possible ECS) machine, wouldn't have AGA capabilities, and has a 68000 CPU. Though a graffiti card would give 256 colors, but only on apps that support it.
Also, the 500 came with AOS 1.3, and needs a kickstart-rom upgrade to go to 2.x. Not sure if there's any 3.x roms for it, though.