However, this was often the premise of these inspiration sites that didn't work out. Wanderfly has the ability to search by number of days and how much money you had to spend, but it didn't really work.
These things are good in concept, but it gets back to my point, that they need TONS of data to make any meaningful recommendations, and that data doesn't exist yet on travel. In many cases music is easier, as a former classical musician I can attest to this, in music theory there are diminished chords, augmented triads, all different types of existing classifications of different types of sound.
In travel it's a big mess. You need big data solutions to sort through the problems, and just building a pretty interface won't solve it, which is what most of these companies have been doing.
- Skyscanner, as David says - Adioso (YC W09) - TripCommon - you can also set up alerts 'SF to Europe for less than $Y00' - Getgoing (YC S12) - Kayak explore
I've always found Skyscanner has the best results, but I'm curious to see how newcomer Getgoing compares.
Google Flights has something similar, it lets you see prices for destinations: