Can I use HTC or ANDROID keyword in my domain names (like htcapps.com or androidfroyo.com)? Are those keywords trademarks?
HTC and ANDROID are both trademarks. You would need express permission to use either in a domain name unless you want to risk having the domain taken and/or sued.
I have one more question, I have contacted Google and HTC, but at my "android" domain I have established website. I write that in contact form when I was asking for permission. Should I leave website on this domain or remove it until I get permission?
If you don't have a major user bases the safest bet would to just make it temporarily unavailable, the last thing you want is to end up with a lawsuit on your hand. They could force you to give up the domain names if they want so make sure your email is extremely nice and you tell them that they can put any terms and conditions they need to if they let you use it.