Floppy Controllers

Modern computers tend not to have floppy drive controllers, so alternative ones are needed. Even in the rare case where your computer has a floppy drive port, it'll really only support native IBM PC formats, and one of the benefits of alternative controllers is the ability to image non-IBM formats on IBM disk drives.

USB Controllers

Name	Drive support	Formats	License	Price	Available	Write
Kryoflux	3"/3.5/5.25"/8"	Many	Commercial*	~$139	?	Yes
SuperCard Pro	3.5"/5.25"	Many	Commercial	$99.95	?	Yes
FC5025	5.25"	Many	Commercial	$55.25	Yes	No
DiscFerret	3.5"/5.25"/8"	Many	GPL/Apache	N/A	No	?
FluxEngine	3.5"/5.25"	Many	MIT	N/A	DIY	Yes
ArduinoFloppyDiskReader	3.5"	Amiga	GPL	N/A	DIY	Yes
USB FDD@1306	3.5"	1.44mb IBM	Commercial	~$13.50	Yes	Yes
Applesauce	3.5"/5.25"	Apple	Commercial	$225-285	Yes	Yes
Virtual Floppy	8"	TRS-80	?	N/A	No	No
SIO2PC	5.25"	Atari 8-bit	Commercial	$35-70	Yes	Yes
X1541	5.25"	C64	Public domain	N/A	DIY	Yes
Glasgow	3.5"/5.25"	Several	BSD/Apache	N/A	No/DIY	Yes
bbc-fdc	3.5"/5.25"	BBC/ADFS/DOS/C64	MIT	N/A	DIY	No

At this point, non-USB ones are pretty much only historical in nature.

Non-USB

Name	Drive support	Formats	License	Price	Available	Write	Interface
AFR	External 3.5"	Amiga	Non-commercial	N/A	DIY	No?	Parallel
Catweasel	3.5"/5.25"	Many	Commercial	?	No	?	ISA/PCI/Zorro
Copy II PC Option Board	3.5"/5.25"	Many	Commercial	?	No	Yes	ISA