Google Keyword Planner is still the best tool to get your keywords but i use it with Long Tail Pro and using Google AutoComplete and auto suggest to find relevent and Latent Sementic Keywords.
Man, if Google Adwords is there then to search on others. It is the best tool to find out the best keywords related to the website in which you are working. Finding the best keywords by viewing its competition and diversity could help you to work on it strategically.