alt Hacker NewsI'm a big fan of the basic power of two choices hash table design. It's simple to understand and implement, has reasonable constant factors, and hits high load factors on real world datasets.
You can use more elaborate probe and relocation schemes, but just choosing the less full bucket and resizing if both choices are full gets you surprisingly far.
Power-of-two length is also the natural choice for a growable linear array where the designer has no idea how many elements there will be.