A bit over 500GB, not counting redundant backups. All are backed up to a 1TB NAS with Level 5 RAID which is now just about full and will shortly be replaced. Backup is also to an external drive. I also have a set stored at the place of a friend, and now and then we swap drives so offsite storage is pretty much continuous.
Offloading from the card is followed by immediately backing up the images, prior to reformatting the card. Then I use drag-and-drop to sort them into logical categories using ACDSee Pro. It also allows me to set up hierarchal categories, with sub-categories for specific shoots or topics. If an image fits in multiple categories, there is no problem dropping it in all. The files are not physically moved or duplicated, it simply sets up pointers in its internal database which makes finding an image very quick. As well as visual searching via categories, one can search on date or any other criteria such as EXIF data. I could easily do a search of all images shot at ISO6400 or higher during August 2009, for example.
Film images have all been triaged, and the best are stored in archival sheets in 3-ring binders by topic. Other negatives and chromes are stored in the sleeves as they came from the lab, in boxes sorted by date. They probably will never be accessed, but are there if access for any reason became necessary. Favorite images have been scanned, and now images are only scanned as needed. Colour prints from my portfolio are stored flat and in the dark, but some of the earliest are showing considerable fading. They have been scanned and restored and in some cases, restored to a higher level than the original print on the day it was made.
All scans are backed up just as the original digital camera images. In the beginning, I used CDs moving to DVDs as soon as they became viable. I do have a BluRay burner, but at the moment hard-drives are the most economical means of making multiple backups efficiently. Now that the price of BluRay media has dropped, I may eventually use them for off-site storage.