you should be able to just make 2 (or more) A records for the same thing pointing to 2 (or more) IP addresses:
Code:
www IN A 192.168.0.1
www IN A 192.168.0.2
...and so on.
For mail, give all of your mail servers the same preference:
Code:
IN MX 10 mail1.mydomain.com
IN MX 10 mail2.mydomain.com
mail1 IN A 192.168.0.2
mail2 IN A 192.168.0.2