Today, while I was ordering a new keyboard for my laptop (a 1-year-old is very hard on them), I ordered a 4GB SDHC card. When it arrives, I plan on expanding FreeBSD's support for SDHC. I had been waiting for the card to arrive to post this, but so far it has taken two weeks and no SDHC card. I bought it on ebay, but the buyer was located in Hong Kong, so my card is now stuck in customs. Let this be a warning to others.
The SDHC card implements the SD Card's 2.0 specification. It is unclear to me if the only change is in the commands sent to the card, or if additional hardware support is required to make things work.
I'll keep everybody posted.