If you wish to be able to read the card from your PC and not simply use it a a big EEPROM here's an extensive thread on the Arduino forums which explains how to interface with an SD card with FAT support.

Also take a look at this Arduino skectch to get you started on the software side. A lot of it has nothing to do with SD card I/O but I'm sure you'll figure it out : ht tp://docs.google.co m/Doc?id=dqhc6fg_0gmk96kdd

There are also couple of hardware solutions which should be usable with Arduino:

1. DOSonCHIP which is FAT32 & FAT16 compatible. It will be really cool when they update the firmware to support I2C SparkFun also has a breakout board for it.
2. 4D systems makes micro-DRIVE. Also this seems to be be available from SparkFun.
3. GHI Electronics has uALFAT MicroSD Board. It has an easy I2C interface and also supports long filenames.

yes it is check this out Arduino SD card

Look at this: Libelium SD module ; check "Documentation:" section, there you will find everything you need.

I used this module, you can even build it yourself. It works perfectly and you have developed libraries for use FAT as you can see.

Saving data on a SD card is not that difficult without premade boards/solutions but saving data on a filesystem (meaning that you can just mount it as a regular partition on your computer) on a SD card is much harder because you have to be able to manipulate the filesystem itself which is much harder, but there are readymade libraries for this which make it easier. So it depends on what you want to do.

You can get a simple SD card reader/writer from the Maker Shed. You can get an SD card reader/writer with audio out with the Adafruit WaveShield.