I have an SE/30 and want to get some software off of vintage-software internet sites. The machine does not have an AppleTalk card, Ethernet card or even a modem attached. What is the best method of getting software from these websites to the Mac' ? ( I have tried an old MacAlly USB-attached floppy drive, attached to my Windows 7 system to generate a 1.4M floppy, but the SE/30 (OS 6.0.1 and 7.1) will not read data on the generated floppy, and insists on initializing it).
No additional hardware is required. The SE/30 has a high density floppy drive that is compatible with USB floppy drives.
In System 7.1, you cannot read FAT-formatted disks by inserting them in the Finder. You need to use the Apple File Exchange application that comes on one of the supplemental system install disks.
System 7.5 introduced PC Exchange, which allows FAT floppies to be mounted in the Finder.
If you don't already have Apple File Exchange or System 7.5 with PC Exchange, you can write a Mac-formatted raw disk image containing them to a floppy using Windows and your USB floppy drive.
You can either download raw disk images containing the software you desire or create them yourself using HFVExplorer. HFVExplorer can also write the image to the floppy for you.
I have heard of people who couldn't get HFVExplorer to write to physical floppies. The program is very old and the source code is lost. But if it fails, you can use any raw disk writing tool you want once you have the images prepared. HFVExplorer may be convenient in that it (probably? iirc) supports Disk Copy images that you would otherwise have to strip the header from.
Happy to be shown wrong by other answers, but I suspect you're going to need some additional hardware. Some options I see:
Low level floppy controller
The controllers on the USB floppy drives available these days tend to only support a narrow range of DOS formatting and not much else. These show up as drive letters in Windows and are convenient to use but not very powerful.
However there are a number of projects that provide special hardware that is also USB but use their own apps to actually access the disks — i.e. it won't show up as a "drive" but instead you use custom utility programs to read and write raw images to the disks. Check out Greaseweazle or FluxEngine or SuperCard Pro for examples. There may be information on their forums or other blog posts on a good workflow (including suggested utilities) for taking the vintage software downloads you have and converting them to the disks you want.
Another trick is to actually replace the floppy drive in your SE/30 with something that reads off a USB flash drive or SD card! In this case you buy a GoTek floppy emulator (physical hardware) and replace its factory firmware with something like FlashFloppy or buy an HxC license.
Then you can configure the GoTek to act just like the original floppy drive did, but instead of using actual floppies you stick in a flash drive full of disk image files and the Gotek lets you choose one of them at a time for the SE/30 to see.
Both of these options (the "raw" floppy drive controller, or the "fake" floppy drive) have pretty good support for common emulator formats, that is if there is a forum full of people who like to play games in an SE/30 emulator then there's probably also a utility available to convert from the emulator format to the type of file that the controller or aftermarket GoTek firmware support.
Macintosh from between eras
Otherwise can you get your hands on a Macintosh that still has a floppy, but was released in the days when the Internet was becoming well supported?
I used something like a Power Macintosh 5200 LC or Performa 5430 in the opposite direction once, to make a backup of some of the original wiki HyperCard stacks. The machine I had was new enough to have an ethernet card available and run a version of Netscape that could post a file to a basic HTML form. But it was old enough to have the floppy drive and understand its old formatting.
While many current download sites probably don't render well on older browsers, and you might have issues extracting the compressed downloads or similar, but in the worst case you can do all the processing on a modern computer and set up your own very simple plain HTML page with links to the files you need.
Cable and special utilities?
There may also be software (names like "Kermit" and "Laplink" come to mind) that works with one of the serial/AppleTalk ports to send files back and forth with one half supported on modern computer hardware/OS. See e.g. https://www.macintoshrepository.org/articles/35--connecting-two-macs-with-a-serial-connection or https://www.reddit.com/r/VintageApple/comments/eeu78e/is_it_possible_to_send_files_to_mac_se_via_serial/.
You'll still probably need to purchase at least one sort of cable and/or adapters (e.g. a USB to serial converter) and there's a bootstrapping problem here because you'll need to get at least one program — the file transfer utility — onto the SE/30 before you can use that to load all the other content.