What are the brands on the market that deliver the results in course racing and speed events?.
You could do worse than a scan of the fastest results in www.gps-speedsurfing.com/default.aspx and see what fins are being used.
I know that the regulars at Sandy Point here in Vic tend to prefer the KA speed fins. They are not only effective speed fins but their rake means that they are good if there is weed around.
Highly recommend KA Speed fins,i own a 23 symmetrical and a 20cm asymmetrical and you cant beat em,never ever spin out in the worst of chop,great for sea weedy places too and very very quick.
Seems to be alot of good speed fins on the market at the moment.
Ive been using the C3 Venoms for a couple of years now and haven't looked back since a mate loan me one. I havnt had a chance to use one of the C3 strikes which are assy fins. no real need for them at my local spots.
Slaloms fins I also use the C3 Venoms or the Stings had very good success on both.
The heavier sailors would prob prefer the Stings More lift but not as forgiving.
other slaloms fins Ive like are the Techtonic Goldwings or Mirages.
Racing-
Deboichet, Tectonics, Vector, Select, C3, Choco, MFC.
Speed-
KA, Lessacher, Tectonics, C3, Select.
Pretty much all fins work otherwise they wouldnt be produced. You need to look at what you are using it for- do you like stiff fins or soft, are you hard on the back foot, is the course tight or broad, is it long or short reach slalom, do you want good range from a fin, are you sailing powered up, is there weed etc.
Personally I been more than happy with the new Select's and I've tried and wasted a fair bit of money on alot of fins now. Of the above I havent tried Deb, KA or Lessacher but obviously I havent tried all of the fins from each brand which changes things alot. My current quiver is-
Speed 23-27 Caspars (havent tried them yet, I trust Brads word that they are good- we seem to have similar taste in fins)
Slalom 29-37 SL/S09's (bit more downwind & powered up biased but generally awesome fins)
Slalom 39-51 S10's (still waiting on these, have tried them though- changed from tectonics talons)
I agree with pretty much all said above, but would add that the Time Machine assy speed fins TM45 V7/V8 and TM48 are sensational, especially on a tight'ish speed course. I feel the V8 and to a lesser extent the V7 are better suited to larger riders than me, but for my size the TM48 is perfect.
The TM Speed 26 symmetrical fin is in a class of it's own as an Alpha fin in 20-25 knots of wind. Good luck trying to get any new TM's though as they are (hopefully temporarily) out of production at the moment. If you can pry a second hand one away from its owners clasp, maybe with large offers of cash, you will do well. 
I have been trying some Lessacher Duo 30 deg. raked speed fins in 22cm, 25cm and 28cm lately and they have been great for 1 hour runs and Alphas with their moderate weed shedding ability. They are also spin out free and surprisingly quick beam reaching and off the wind, and very stable through the chop. I still don't understand how they work, but they do. 
fogot to mention the select Caspars i use the the select Caspar gps/speed 31cm and i would say they are nearly as good as the KA and there alot cheaper.
Hallo Sailquick! At first: no spin out. I worked asymm. fins not flat leewards.
I worked from the thickest point of profile a2-3mm concave in. That was
only for one way. So we used left and right fins. I tried concaves on both sides, that do not work. Only with the concave can the water not come behind the fin
to the other side , where we have a little vacuum. Thats a big brake.I could
that see on a board with acryl bottum. But always for one way.
There my fins are 4km/h faster was it easy to say. I am first with 4 or the half,
2km/h. So worked I the concave only on one side to the half, for the way back
on the other side, but diagonal. Sorry ,the speed was the same, not slowlier,but why? The concave for the way back, there where we have vacuum,reduce the
vacuum and allow more speed. Döblin made with the Rake 30° fin in 22cm
Topspeed from 50 knots. That was only one of good 20 points that are in my
doubleasymm. fin. Thank you for testing . Wolfgang
Hallo Sailquick! At first: no spin out. I worked asymm. fins not flat leewards.
I worked from the thickest point of profile a2-3mm concave in. That was
only for one way. So we used left and right fins. I tried concaves on both sides, that do not work. Only with the concave can the water not come behind the fin
to the other side , where we have a little vacuum. Thats a big brake.I could
that see on a board with acryl bottum. But always for one way.
There my fins are 4km/h faster was it easy to say. I am first with 4 or the half,
2km/h. So worked I the concave only on one side to the half, for the way back
on the other side, but diagonal. Sorry ,the speed was the same, not slowlier,but why? The concave for the way back, there where we have vacuum,reduce the
vacuum and allow more speed. Döblin made with the Rake 30° fin in 22cm
Topspeed from 50 knots. That was only one of good 20 points that are in my
doubleasymm. fin. Thank you for testing . Wolfgang
follow speed guru,s thanks for the feed back.currently using leading edge carbon and tectonic.It was interesting hearing about fins that do not cavitate under load.
Anybody tried a hydrofoil fin set up ?
