ZX81

NO$ZX81
A freeware ZX80/81 emulator for DOS and Windows.
http://nocash.emubase.de/zx8.htm

T/S 1000 Emulation in a Browser Window
Java emulator of Timex-Sinclair 1000.
http://www.vavasour.ca/jeff/ts1000/

VB81
Sinclair ZX81 emulator written in VisualBasic. Runs under Windows on a 133MHz Pentium or better. Includes source.
http://freestuff.grok.co.uk/vb81/

XTender
ZX80 and ZX81 Emulator Site
http://www.delhez.demon.nl

z81
Open source ZX80/81 emulator for Linux.
http://www.svgalib.org/rus/z81.html

Z80Stealth
A freeware ZX80 emulator for DOS which draws the screen lines by lint, thus fixing some flicker problems seen in other emulators.
http://z80stealth.emuunlim.com/