USB cards don't need drivers but the computer must have at least OS 8.1 to have the system resources to support USB.
For full-size ethernet cards in tower computers, most don't need drivers.
I help a friend keep three 14-year old PowerBook Walstreets in service and we just ordered two CardBus USB cards. They are getting harder to find--the model we manged to find required OS10.2 or later, so you may be on the lookout for cards almost as old as the 1400.
I found his cards on NewEgg and that vendor had only the one modle that was USB only and supported older versions of OSX.
Generally speaking, since CardBus is not supported here, you would have to look for 16-bit PC Cards (PCMCIA).
Sometimes, separate drivers are not needed. Examples include many modems, but also adapters for CompactFlash. In other cases, such as with various networking products, the cards often require special driver software.
I use Sandisk PC Card Adapters on my Powerbooks 540c, 1400, 3400, and 3500. I use Compact Flash cards that slide into the adapters which then are plugged into the PCMCIA slots. No drivers are needed but proper formating is necessary. These are very useful as a bootable external drive or for cloning backups
Google "sandisk pc card adapter" in order to see what is available currently.