$5 WiFi ESP8266 boards. These are complete with USB programming interface. Program them just like an Arduino. Best deal I’ve found. I can’t build them this cheap. Get them while they are hot! - https://amzn.to/2Pv0MEk
Looks like the old (v0.9) NodeMCU layout… it works, without a problem, only - keep in mind, this is exactly as wide as a single breadboard (five rows + center + five rows), so, if you want to use these on a breadboard, you need either at least a double-wide one, or you have to connect your stuff under the board - possible, but not exactly too handy… The newer (NodeMCU v2/v3) layouts are one row narrower on both sides, so you can at least see where you’re plugging your stuff in - guess how I know so well and what board version I bought as my first one 
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No, this is a v3 board and works on breadboards just fine. If you don’t mind waiting for shipping, I bought some for $3 from aliexpress.
@Dale_Farnsworth Ah, my mistake - good to know, thanks. But at the moment, I’ve got more ESP boards laying around than I know what to do with them - what’s missing is the time to really get going with 'em (“So many possibilities, so little time…” )…
I got these in 6 days, here in the US.
Another vendor on aliexpress has them for $2.44 including shipping.
This one with the CH340G usb-serial chip is $2.19. The cp2102 version is more. https://www.aliexpress.com/item/Free-shipping-1pcs-NodeMCU-V3-Lua-WIFI-module-integration-of-ESP8266-extra-memory-32M-Flash-USB/32837826982.html