[curun1r]

I've had good results from kiwi.com. They allow you to use date ranges and will can show a map with fares to various locations. They also include airlines that don't normally participate in aggregators (e.g. Southwest). They also allow multi-leg itineraries, which is really useful for longer trips.

[jpalomaki]

Kiwi also comes up with suggestions to stitch the trip together from multiple, individually issued tickets. This can bring down the cost, but the drawback is that airline is then not responsible for helping you in case of delays and you may need to pick luggage mid travel and check them in again.

[sitepodmatt]

I believe Kiwi underwrites this in that they will rebook you another flight and pay costs incurred hence they pad with long layovers even if a shorter connection is available to reduce the risk exposure. They will probably get better at this over time, it seems at the moment they are quite risk adverse and it's all very manual - i.e. you have to call them to tell them that your flight was late and you've missed second connection.