Here is a list of commands you can type/use:

rcon_password "yourRCONpasswordhere"
RCON stands for Remote CONtrol and in your server.cfg you can change the RCON password, look for the following line:

rcon status
will give you a status of your server with a list of players and their ID's/IP's, very usefull, because by selecting and using ctrl C and ctrl V, you can easily copy/paste a name, ID or IP number. The first list of numbers is a list of userid's. After the list of names you will have a list of uniqueid's and the last list is a list of IP's.

rcon kickid x (x=userid or uniqueid)
kick someone by his userid or uniqueid

rcon banid m x kick (m=minutes ban, m=0 means permanent ban, x=uniqueid)
example: rcon banid 0 STEAM_0:0:123456 kick, player with the uniqueid STEAM_0:0:123456 is now kicked and banned forever.

rcon addip m x (m=minutes ban, m=0 means permanent ban, x=IP)
example: rcon addip 45 212.234.555.346, player with the IP 212.234.555.346 is now banned for 45 minutes. 
In the statuslist you see probably something like this: 212.234.555.346:43621 in order to ban someone using the IP, you must not use the red part in the command.

rcon writeid
this will write a file with all the uniqueid's that you have banned so far. This is necessary once in a while, because if you restart your server, all your banned ID's will be lost if they have not been written in a file.

rcon writeip
this will write a file with all the IP's that you have banned so far. This is necessary once in a while, because if you restart your server, all your banned IP's will be lost if they have not been written in a file.

rcon removeid x (x=uniqueid)
to remove a uniqueid from the file, in other words you can repair what you have done with the command writeid.

rcon removeip x (x=IP)
to remove an IP from the file, in other words you can repair what you have done with the command writeip.

rcon changelevel y (y=mapname)
this will change maps, here is a list of original mapnames:

cs_italy
de_dust
de_aztec
de_dust2
cs_office
de_chateau
de_cbble 
de_piranesi
cs_havana

rcon mp_restartgame m (game restarts in m seconds)

rcon say "blablabla"
if you want to talk to everyone on the server, you can use this option.

rcon killserver
this will shut down your server.

The next list of commands can also be used in your server.cfg. If you scroll up with your mouse you will find a chapter called server.cfg and in it some explanations of the following commands...
BUT be aware that after every mapchange your server.cfg is loaded again, so every change you've made using rcon is lost in a new map!:

rcon mp_timelimit 45
rcon mp_winlimit 14
rcon mp_maxrounds 21
rcon mp_roundtime 4
rcon mp_freezetime 4
rcon mp_buytime 1
rcon mp_startmoney 800
rcon mp_c4timer 35
rcon mp_flashlight 0/1
rcon mp_footsteps 0/1
rcon mp_autoteambalance 0/1
rcon mp_limitteams 0/1
rcon mp_friendlyfire 0/1
rcon mp_tkpunish 0/1
rcon mp_autokick 0/1
rcon mp_forcecamera 0/1
rcon mp_allowspectators 0/1
rcon mp_spawnprotectiontime 10
rcon sv_timeout 40