Swim speed work

See above, very good advice.  Your speed doesn't improve becuase you are not doing any speed work.  100 and 200 yd/meter sets, done at a consistent workin ghard pace are good for building speed.  All you are doing now is teaching your muscles how to go long and slow.

Your form is breaking down because your set length is too long.  Again, shorter sets.  you'll need to find a balance between going fast and maintaining your form though, because most people, myself included start losing form the faster they go.

And remember - speed is NOT gained by pushing harder against the water (the water pushes back just as hard) but by learning proper form so you are gliding through the water.  A lot of people swear by Total Immersion techniques.

I' not sure I see the logic in this.  It seems analogous to cadence on the bike.  You can spin easy but relatively fast or hard with a lower cadence to achieve the same speed/power output.  There are consequences to pulling harder...like potentially burning out your fast twitch fibers, starting to burn off valuable glycogen, and potentially increasing lactate accumulation prematurely.  If I can go just as fast by stroking easier then you better bet that's what I'll be doing.  What exactly are you gaining by "saving" 2-3 strokes assuming your requiring your muscles to work harder to cut that stroke count down for the same speed?  For most of us there is a lot more potential in working on efficiency over brute force in the water.  That being said, I think the OP should start to incorporate shorter intervals and swimming sets instead of just going long.  There is a great little workout guide called Swim Workouts in a Binder.  It's waterproof and has over a hundred specific workouts divided up into categories to focus on endurance, force, muscular endurance, anaerobic threshold, etc.

Not a p[ic but here is a good description of the sewing machine:

http://forum.slowtwitch.com/gforum.cgi?post=782744;sb=post_latest_reply;so=ASC;forum_view=forum_view_collapsed;;page=unread#unread

I actually just found that ST thread yesterday...had never heard of the sweing machine dril before.

Yet another swimming speed debate If you want to swim fast you HAVE to practice to swim fast, period. Yes technique is very important but at some point you trade prefect technique for a bit more of strength/endurance and be able to get yourself through the water faster than your competition. To achieve this you have to find your right balance between DPS (distance per stroke and SF (stroke frequency)

There are world champion swimmers who can swim equally fast but with different styles. One might glide a bit more and have a better DPS while the other might have a higher SF. So there is NOT a single way. BTW, I think that the emphasis suggested on “efficiency” and drills sometimes is pointless unless you have a coach accessing your swim.  Granted it is important but you need to get feedback to know you are doing it correctly and NOT reinforcing bad habits. Finally, if I have to choose between swimming pretty and “efficient” or ugly and fast I’ll definitely pick the latter

Anyway for the OP, here are a couple of killer workouts for speed and adjust depending on your level:
WU: 300-500 drills done as 25 drill 25 swim, MS: 20-40x50 as odds done all out with 10-15 sec rest/ evens done with kickboard mod/hard with 15-20sec rest, CD: 4-8x50 swim golf

WU: 300-500 drills done as 25 drill 25 swim, MS: 10-20x100 at race pace (i.e. if you want to avg 1:20 per 100 on your race shoot for that speed) rest 10-20 sec in between CD: 200-400 easy bilateral breathing

This is more to simulate race swim (speed/endurance) >> WU: 300-500 drills done as 25 drill 25 swim, MS: 3-5x500 continuos swim done as 100steady/100hard with 1 min rest in between, CD: 200-400 easy DPS

I DONE THAT DRILL!!! The "sewing machine" drill and loved it. BUT for those fans of TI it will go against of what they have learned… pretty much it teaches you to keep your recovery short, and to improve your stroke count while keeping the recovery with high elbow and to begin the pull from your forearm. GREAT drill

two great drilsl for strengthening your forearms are fist and doggy paddle. doggy paddle does what it says on the tin and is suprisingly hard. fist is normal free but with closed hands; this improves the strength you get out of the forearm rather than just your open hand.

that set sounds amazing! i'm gonna print it off and give it a whirl asap. well once i've done my sponsored swim to send a girls footie team to the outgames in montreal. ta loads

the point being, for a newer swimmer, that shear brute force alone does not increase your speed without proper technique.  Many folks do not know this