Contact
...how to reach me.
Accepting mails at radek@podgorny.cz.
When possible, I digitally sign the messages. You can encrypt, too. For any of these two operations, my public key may come handy (see below)...
If you've sent me something and I didn't reply in reasonable time, there may a be a problem with mail delivery (to you). See UndeliverableMail if this is your case.
jabber
My jabber id is radek@podgorny.cz (this is NOT an email!)...
My current status: 
The digital signature and encryption part applies to jabber as well. The key is the same...
ICQ (or AIM, MSN, etc.)
I do not use it, use jabber.
Why? Proprietary protocol, insane license (go ahead and read it), you got the idea...
cellphone
...hm, will tell you only when asked via one of the above media (or personally). 
skype
...is shit, therefore I do not use it! The protocol is proprietary, the program is closed-source, you name it...
GPG (free compatible PGP implementation)
Here comes my public OpenPGP key.
(Fingerprint: D177 4B08 C595 8180 E787 E218 EE67 A3EA 98E5 6D84)