This is uncanny, I had the very same idea just today, it's about time a thread like this was started. I have to agree with you about the Kickstart ROM switchers from AmigaManiac, I have one of each of the two models in an A500 and an A600 and they're great. The build quality is top notch, as was the service, but the price was dirt cheap.
I guess we should add a few products that are currently available from several resellers, which are either still in production or have had recent product runs. To be fair, I think we should try to link to as many places that sell this hardware as we can find. I know there are definitely a few smaller, regional stores still selling Amiga stuff around the world that might appreciate some new customers.
Maybe as people post new links to hardware, you can edit the original post to include all the links for easy future reference.
I think by now a lot of people know that GVPm have just made a new run of A1200 030 accelerators, RAM, and possibly accelerators for A2000/A4000 to follow. I'm pretty sure Software Hut sells them.
The A603 seems to be out now, and will give A600 owners twice as much Chip RAM (2mb), a Real-Time Clock, A1200-style Clockport (for further expansions such as the MP3@64 or Subway USB cards) and an expansion to allow you to fit the new Indivision ECS Scan Doubler/Flicker Fixer when it comes out.
Speaking of the Indivision, these things are AWESOME. I have one in this A1200, and it allows me to browse the web without having to scroll sideways on every website by giving me a 1024x768 resolution. They are now available for all A1200 revisions, A4000D and CD32. The Indivision ECS is in development, and should end up being slightly cheaper than the Indivision AGA.
We definitely have to mention the NedoPC A600 8MB Fast RAM card, which is available for preorder through Zetr0 on the English Amiga Board. These expansion cards plug into the CPU of your A600 and allow it to use a full 8MB of Fast RAM, or 5.5MB if using the PCMCIA slot. These are the famous Russian RAM cards that were so hard to get hold of until recently.
There was a recent new run of Subway USB cards too, which I am proud to own myself. These puppies let you use just about any USB device you can poke at it if you have an Amiga with a Clockport and a 030 using the bundled Poseidon USB stack. Using the Anaiis USB stack, you can use mice, keyboards, gamepads and USB printers on any Amiga (68000 included) with a Clockport. The Subway, bundled with an OEM copy of Poseidon is available from AmigaKit.
There's a bloke out there building Playstation-CD32 controller adapters, which let you use a Playstation control pad for any Amiga joystick/pad/mouse game. Only thing is, he doesn't sell them from an online store.