Conky

Conky is a free, light-weight system monitor for X, that displays any kind of information on your desktop.

Conky can display more than 300 built-in objects, including support for:

• A plethora of OS stats (uname, uptime, CPU usage, mem usage, disk usage, "top" like process stats, and network monitoring, just to name a few).
• Built-in IMAP and POP3 support.
• Built-in support for many popular music players (MPD, XMMS2, Audacious).
• Can be extended using built-in Lua support, or any of your own scripts and programs (more).
• Built-in Imlib2 and Cairo bindings for arbitrary drawing with Lua (more).
• Runs on Linux, FreeBSD, OpenBSD, DragonFlyBSD, NetBSD, Solaris, Haiku, and macOS!
• Docker image available for amd64, armv7, and aarch64 (aka armv8)

... and much much more.

Conky can display information either as text, or using simple progress bars and graph widgets, with different fonts and colours.