The current CF+ 4.0 specification supports IDE DMA133 for a maximum throughput of 133MB/s, yet very few cards are able to hit that kind of speed.
Transcend has recently announced a couple of 600x-capable CF cards in 8GB and 16GB capacities. As speed is derived from a base 150MB/s throughput - a la CD-ROM - Transcend is claiming peak 92MB/s read and 87MB/s write speeds.
The 'Extreme Plus' cards use a quad-channel controller, via UDMA6, and tasty Turbo MLC memory to hit the speeds, and they're reasonably close to low-end SSDs in pure sequential performance.
The next iteration of Compact Flash cards, due in late 2009, will use a new interface, CFast, and be based on the SATA protocol, so these may well be the fastest cards for a while yet.
No word on pricing just yet but they do look tasty for dSLR users.