I personally have a Western Digital Mybook 1 TB, and a LaCie 250 Gb portable. Both I have used a lot (video editing with the LaCie and torrenting 24/7 for weeks on the MyBook) for about a year now. And so far I've had no problems with the WD, but I lost 40 Gb of video on my LaCie at once for no reason while I was in the middle of a rendering.
I prefer WD, and at home we have 2 other WDs, which have never failed. Only downside is you get only a 1-year limited warranty. The other brand I would recommend is Seagate. They offer excellent and reliable drives, and are so full of it that they give you a 5-year warranty. On a hard drive this kind of thing matters. But I think they are a little more expensive, I haven't ever bought one.
I think you should check out WD and Seagate, and depending on the size, portability, connections you want choose accordingly to your price range. But these two brands will get my respect forever. And I suggest not to buy from an obscure and unknown company, because their drives might really well fail more often.
Finally, I think you should really do backups of your stuff. Either go RAID on your ext. hard drive, or manage to buy 2 and get one to be the exact copy of the other, but always turned off and stored except when doing the backup. In case your ext. drive fails, you go in your closet and have another one exactly the same to whip out.
