I've just got one-wire to work on my Carambola. It only requires a single extra pull-up-resistor on a GPIO (I used an 1K to the 3v3 power supply) and a fairly small patch to the linux-kernel.
patch on the kernel. If the kernel source isn't there yet, you may need to run 'make' to get it.
patch -p1 </location/of/downloaded/diff/carambola-w1.diff
Then run a 'make kernel_menuconfig' and make sure to select 'machine selection -> Ralink RT350x machine selection -> Enable 1wire support on GPIO14'. If you want different drivers, also look under 'Device Drivers -> Dallas's 1-wire support' and select what you want. Then re-build openwrt by running make, and install the resulting firmware image to a Carambola. Finally, solder the pull-up between GPIO14 and 3V3, connect some one-wire devices between GPIO14 and ground and start the Carambola.
Now you should have a dir in /sys with all the attached one-wire devices in it. Cat 'w1_slave' in the directory to see what the device returns. For example, I have a string of 5 DS1820 temperature sensors connected to it. As you can see, at the moment it's about 21 degrees celcius in my room:
root@OpenWrt:/# cat /sys/devices/w1\ bus\ master/10-000800*/w1_slave
2a 00 4b 46 ff ff 0f 10 40 : crc=40 YES
2a 00 4b 46 ff ff 0f 10 40 t=20812
2a 00 4b 46 ff ff 0b 10 7b : crc=7b YES
2a 00 4b 46 ff ff 0b 10 7b t=21062
2a 00 4b 46 ff ff 0d 10 d1 : crc=d1 YES
2a 00 4b 46 ff ff 0d 10 d1 t=20937
2b 00 4b 46 ff ff 07 10 75 : crc=75 YES
2b 00 4b 46 ff ff 07 10 75 t=21312
2a 00 4b 46 ff ff 0a 10 bf : crc=bf YES
2a 00 4b 46 ff ff 0a 10 bf t=21125