Incomplete Guide to Airfoil Usage
If you're working on reproducing a design but don't know what airfoil it uses, the
answer is probably here. Part of the UIUC airfoil data site.

UIUC Airfoil Data Site
Public access airfoil section shape database.

MIT ACDL Resources Page
Software resources including X-Foil.

Profili 2
Freeware graphical front end for X Foil including large foil database.

Jet Engine Specifications Database
Best source I've ever found for jet engine data, very complete.

Prime Mover
Excellent starting point for researching piston engine specifications and details.