Firm websites may seem similar, but if you look closely enough or at the right things (Chambers & Partners, localized Vault guides, NALP data, ATL, AmLaw, etc.) you can see that every firm has its own niche(s) and characteristics. The key is to start from a goal and find which firms will help you meet that goal. Do you want to work in the most sophisticated SCOTUS practices in the country? Ok, well go see Jenner & Block, GDC, Sidley, Williams & Connolly, Wilmer, Kirkland, Jones Day, and a few others. For international corporate work, the leading NY firms are probably best. Communications law? Check out Wiley Rein. CFIUS? Skadden has a great practice in that area -- though they're hardly the only ones.
I could go on for a while, but if you do your homework, you'll start to see that the firms are nowhere close to the same. The fault lines are not only work or practice-based. Firms differ along cultural lines as well, with some firms carrying a more "fratty" feel (see, e.g. SullCrom in NY or Latham in many of its offices), while others feel more reserved (Williams & Connolly comes to mind). Some are 24/7 in your face (Skadden), others more relaxed -- at least as a relative matter (Quinn). Some firms are more family friendly than others (there are rankings for this somewhere), and so on and so on.
You have to weigh all of these things, plus financial stability, pay, benefits, and hiring criteria, to find which firms are going to be best for you. It is not an easy process, but if you do your homework over the summer, the effort will pay off in spades come fall. I prepared a spreadsheet listing each of the factors I cared about and populated it with data from the above mentioned sources. That made it easier to compare the firms in a straightforward fashion. If you really get to know the firms and can tell a coherent story as to why you want to work for them, you can interview well above your GPA. If, on the other hand, you treat the firms like they're all just an undifferentiated mass, they might end up treating you like just another random law student...
EDIT TO ADD: Here's a list of links I just sent to someone in a PM, but I think it'd be useful to othersAbove the Law
(use the search function to search for the firm, market, or practice area you're thinking of)Chambers and Partners USA
(use this to see which firms are best in a given practice area, either nationally or in a particular market. For instance the best antitrust firms in DC are here: http://www.chambersandpartners.com/Edit ... ssid=27908
(use this to search to see which firms hire in your desired market(s), which firms focus on which practices, how they allocate attorneys between practice areas, how large their workforce is, what a firm's leverage is, etc.)Vault
(lots of info on firms here, though your career office should have more localized guides available either in print or PDF)AmLaw surveys & rankings
(tracks layoffs and other bad stuff happening at firms)