The motto from Field of Dreams
If you build it, they will come!
is often seen as the wrong attitude towards building web applications in general; its variant "If you publish it on the web, they will come" often works for research data, though. And what's even better they may provide added value on top of your data!
the WALS Sunburst Explorer, an online visualization tool that combines areal and genealogical information of the WALS database