I almost never stay at the hotel in which the conference is at. I look for a lot cheaper one close to the location where the event takes place and this way I save a lot of $$. Even if you have to rent a car (sometimes you can just use the local public transportation system), you can still save money. Another way is to make smarter choices when it comes to where you eat. If you have a small kitchen at your room, you can buy and prepare the food you will need on your own. Also there might be times where you know someone who will be attending the same event as you and this way you can split the cost of the room and transportation.
I hope this gives you some extra ideas.