We have seen modular interlocking rubber tiles that we would like to use but they cost way too much. Any ideas?

I have grass in mine with a covered area of cement for her dog house and bed. She loves it in her kennel and seems to always be comfortable whether it's hot or cold. The only problem with dirt is that it turns to mud and that's not very fun for you to deal with. Sand has similar problems, but not nearly as bad.

Personally I like semi-packed dirt. I find that sand blows away MUCH too easily and that cement is cold and harsh. One of the main advantages of dirt is you can easily poop scoop. Just scrape/dig and throw away. The negative to dirt is that many dogs like to dig, so on the farm I worked on we had poured cement and then dirt on top of that.

we put wool blankets although we have Siberian husky. I think anything that they can snuggle up with will help them stay warm, and maybe put a blanket over the kennel depending on if its enclosed so not to keep the wind out.

Cement they can't dig out. Easy to clean.

Have a look at this. http://cgi.ebay.co.uk/Cattery-Dog-Kennel-and-run-8-x-4_W0QQitemZ260202565437QQihZ016QQcategoryZ1284QQss PageNameZWDVWQQrdZ1QQcmdZViewItem#ebayphotohosting

i recommend you put your dog in it.

I guess whatever would be more comfortable and reasonable, like grass or matts. CHeck out more kennel training at http://www.kidsandtheirpets.blogspot.com

Gravel is relatively inexpensive and much better than any of the options you mentioned.

Personally I build raised decks under my runs using that plastic composite lumber they use for decks. It is easy to clean, is very durable, prevents digging and provides great drainage....the down side is that it is expensive.