BSD things
All things *BSD I stumbled upon that might be useful without having to remember them all. :-)
List all executables starting with a specific character (in csh);
Type the character, for instance "d", in the shell, then do Ctrl-d to get everything starting with d:
dell02% d
daemon
db_deadlock-4.2
dcopserver
discovermacro.pl dumpreg
date
db_dump-4.2
dcopserver_shutdown
diskinfo
dvd+rw-booktype
db41_archive
db_dump185-4.2
dcopstart
disklabel
dvd+rw-format
db41_checkpoint
db_load-4.2
dd
display
dvd+rw-mediainfo
db41_deadlock
db_printlog-4.2
ddbugtopbm
distcc
dvd-ram-control
db41_dump
db_recover-4.2
default
distccd
dvdauthor
db41_dump185
db_stat-4.2
derdump
distccmon-text dvdbackup
db41_load
db_upgrade-4.2
designer
djpeg
dvddirdel
db41_printlog
db_verify-4.2
desktop-file-install
dmesg
dvdunauthor
db41_recover
dbus-binding-tool
desktop-file-validate
dmidecode
dvi2fax
db41_stat
dbus-cleanup-sockets
devd
dmp
dvicopy
db41_upgrade
dbus-daemon
devdump
dnsextd
dvigif
db41_verify
dbus-launch
devfs
dnssec-keygen
dvihp
db42
dbus-monitor
devinfo
dnssec-signzone dvilj
db4_archive
dbus-send
df
domainname
dvilj2p
db4_checkpoint
dbus-uuidgen
dga
dprofpp
dvilj4
db4_deadlock
dc
dhclient
drkonqi
dvilj4l
db4_dump
dconschat
dhclient-script
dropdb
dvilj6
db4_dump185
dcop
dialog
droplang
dvipdf
db4_load
dcopclient
diff
dropuser
dvipdfm
db4_printlog
dcopfind
diff3
dsirc
dvipdft
db4_recover
dcopidl
dig
dtmfdecode
dvipng
db4_stat
dcopidl2cpp
digictl
dtsdec
dvired
db4_upgrade
dcopidlng
dirmngr
du
dvitomp
db4_verify
dcopobject
dirmngr-client
dump
dvitype
db_archive-4.2
dcopquit
dirname
dumpfs
db_checkpoint-4.2
dcopref
dirs
dumpon
dell02% d
More than one character is also possible:
dell02% mo
moc
mount
mount_linprocfs mount_nfs4
mount_procfs mount_umapfs
modutil
mount_cd9660 mount_linsysfs
mount_ntfs
mount_reiserfs mount_unionfs
mogrify
mount_devfs
mount_mfs
mount_nullfs
mount_smbfs mountd
montage
mount_ext2fs mount_msdosfs
mount_nwfs
mount_std moused
more
mount_fdescfs
mount_nfs
mount_portalfs mount_udf
dell02% mo