Many systems are programmable from a PC, but they do need an interface to do this.
I'm not sure there are any 'direct USB boot load and debug' 8051's ?

There are 8051's with RS232 boot loaders, so they come close ?

eg
http://www.stc-51.com/devtools/stc-usb.php

I think that is free with 8051 chip orders ?

Or, they have a more complete Starter Kit here for $25, which seems to include a LCD Module ?
http://www.siliconray.com/index.php...r-kit.html

This uses the STC12C5A60S2, which is a good 40/44 pin starting point.
There is no Single step Debug.



USB connection is universal these days, even if it is via a COM driver.



What cards ?

As mentioned, SlLabs ToolSticks are the lowest cost way to get Programming _and_ debug working to a PC.
Many of their toolsticks have 0.1" grids on them, for expansion.

Next would be probably be Zilog's Z51F - more money, but they do have a Cypress High Speed USB chip in their link. ( How much is your time worth ? )
Not as 'field proven' as SiLabs yet.

Silabs and Zilog are not big on DIP packages, whilst STC do a lot of DIP.


Atmel and Cyrod have Debug systems as 'work in progress',