.
You have many options. You should be able to get away for $100 and have PLENTY of space; jump up to $150 and you can really do well.
Basically, buy a bare drive and an external enclosure for it. Connect to your computer & format drive. You're good to go. If the drive will sit in one place and (almost) never travel, then get a 3.5" internal bare drive and it'll sit happy at your desk & be good. DO NOT get a budget bare drive (like, Seagate green tech drive 1.5 TB for $100) .. they are really failing a lot right now.
So, here's a bunch of options. Currently, it's hard to beat newegg, so I'm gonna link to them for a bunch of specific examples.
Get a notebook/laptop 2.5" drive if you want portability,
and it
will travel better than a 3.5" drive.
Suggest this one as entry level, as the Black edition WD drives are really solid in performance and reliability:
Western Digital Scorpio Black WD3200BEKT
320GB 7200 RPM 16MB Cache 2.5" SATA 3.0Gb/s Internal Notebook
Currently $60 & free shipping
http://www.newegg.com/Product/Product.aspx?Item=N82E16822136280(promo code: EMCYWNV34 will knock another $10 off until 02 Sept, so $50)
Jump up to 500 GB, at the low end. I'd trust this one, so long as I treated it with care & respect:
HITACHI Travelstar 5K500.B HTS545050B9A300 (0A57915)
500GB$50 + free shipping
http://www.newegg.com/Product/Product.aspx?Item=N82E16822145257For $10 more this is awfully solid (you're not really after performance; reliability and using external cable is more important):
Western Digital
Scorpio Blue WD5000BEVT
500GB 5400 RPM 8MB Cache 2.5" SATA 3.0Gb/s
$60 + $1 shipping (this is probably what I'd go for today if I was buying)
http://www.newegg.com/Product/Product.aspx?Item=N82E16822136314Splurge and go to the Black edition (you don't need it, but hey, some extra insurance in reliability; your call):
Western Digital Scorpio Black WD5000BEKT
500GB 7200 RPM 16MB Cache 2.5" SATA 3.0Gb/s
$75 + $1 shipping
http://www.newegg.com/Product/Product.aspx?Item=N82E16822136692You can find 1 TB laptop drives, but be careful: some are off-sized and may not fit external cases. Read dimensions carefully!
Now decide on a case. USB 2.0 is 'Good Enough' but a bit slow-ish for large data transfers. If you have the capacity for eSATA or USB 3.0, definitelty consider it. USB 3.0 will plug into a USB 2.0 port and just transfer at USB 2.0 rates. Plug into a USB 3 port and it will be approximately SATA transfer rates (about 8x faster).
One budget possibility (Rosewill is a newegg house brand & is generally solid budget gear; new egg is great about returns for stuff that don't work in the first 30 days):
Rosewill RX81U-ES-25U3 Aluminum / Plastic 2.5"
USB 3.0 External Enclosure
$18 + $3 shipping
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182236You can go cheaper a little bit if you just want USB 2.0; but the prices are so close that better to go with USB 3.0 and be prepared for the near future.
Wanna go with a 3.5" option ..?
Here's about best $-per-GB option right now:
Western Digital Caviar Black WD7501AALS
750GB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5" Bare Drive
$60 + free shipping (I just bought two of these:
very happy)
http://www.newegg.com/Product/Product.aspx?Item=N82E16822136283I'm a little wary of 1 TB and higher drives right now, but I'd give fairly solid trust to Western Digital 1 TB, either blue or black edition.
This one's about as robust as it gets; it's actually better used as a performance drive inside your PC. That 64MB of cache is a sweet performance boost that's a bit wasted on an external (as is 7200 rpm):
Western Digital Caviar Black WD1002FAEX
1TB 7200 RPM
64MB Cache SATA
6.0Gb/s 3.5"
$90 + free shipping, plus -$10 w/ promo code through 01 Sep
http://www.newegg.com/Product/Product.aspx?Item=N82E16822136533HOWEVER, notice it's a
SATA III drive (
6 GB/S). Make sure your enclosure handles both that speed and the large capacity. Most handle 1 TB as a standard right now, but if you go for a 1.5 TB or a 2 TB, some enclosures won't do it.
However, this drive over USB 3 &/or eSATA will definitely scream data down the wire like nobody's business.
Here's a possibility for a docking station that handles USB 3, SATA 6 GB/s, and both 2.5" and 3.5" drives:
EAGLE ET-CSKSU3-BK 2.5" & 3.5" Black
USB 3.0 Docking Station
$30 + $7 shipping
http://www.newegg.com/Product/Product.aspx?Item=N82E16817193076If you don't intend to keep the drive out all the time, this is a possibility. Keep your drive in storage and plug it into the docking station when you need to access or write data. Advantage here is versatility rather than convenience.
A more robust desktop enclosure:
Rosewill RX35-AT-SC BLK Full Aluminum Cover, Metal Tray 3.5" Black
USB2.0 & eSATA$25 + $3 shipping
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182180Only USB 2.0, but if you have eSATA, this could do you well.
Confused you with enough options yet ..?

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EDIT: I made three recent posts that cover some other details on this topic you might want to check out:
-
http://forums.bakabt.me/index.php?topic=25835.msg4487473#msg4487473 -
http://forums.bakabt.me/index.php?topic=25835.msg4488033#msg4488033 -
http://forums.bakabt.me/index.php?topic=5771.msg4487546#msg4487546 ]