I always forget this:
ELV Exremely Low dc - 3khz
VLF Very Low Freq 3khz - 30khz
LF Low Frequency 30khz - 300Khz
MF Medium 300Khz - 3Mhz
HF High 3mhz-30mhz
VHF Very High 30mhz-300mhz
UHF Ultra High 300-3Ghz
SHF Super High 3Ghz - 30 Ghz
EHF Extremely High 30Ghz - 300Ghz
Saw Panther had an auto-encrypting folder, which is pretty cool. OpenBSD has cryptdir, but it uses crypt, which means passing a password when logging in and logging out. I wanted it to use gpg, so I wrote lockdir (the correct solution is to extend cryptdir).