Hardware Secrets posted a review on the ASUS P7P55D PRO motherboard, which has lots of unique features and includes support for SLI. Here's an excerpt:

The most obvious advantage is the support for SLI, the presence of three x16 PCI Express 2.0 slots (although they run at lower speeds when more than one video card is used) support for RAID, use of only solid capacitors and a high-end voltage regulator. It also brings the unique memory compatibility test (MemOK!) and way more overclocking options than other boards on the same price range, plus the interesting idea of adding a physical switch for limiting memory overvoltage and thus preventing users from frying their CPUs.

Another highlight from ASUS P7P55D PRO is its professional grade on-board audio, which will allow you to edit analog audio sources without practically non-existent white noise, due to its high signal-to-noise ratio (100 dB). Translation: you can use this board to professionally edit audio without the need of buying an add-on sound card.

But we missed some small features on P7P55D PRO that are available on competing products, like a POST diagnostics display, an external clear CMOS button (or at least an on-board clear CMOS button), on-board power and reset buttons and a buzzer.