1. Load Factor: A low load factor is not especially beneficial. As load factor approaches 0, the proportion of unused areas in the hash table increases, but there is not necessarily any reduction in search cost. This results in wasted memory.
  2. Separate Chaining: linked list in the the given bucket
  3. Open addressing:  linear probing(probe =1) , quadratic probing (probe = quadratic function), double hash(probe is calculated using another hash function)
  4. Coalesced hashing: mixture of chaining and open addressing
  5. Robin hood hashing:



More information at http://en.wikipedia.org/wiki/Hash_table#Collision_resolution