Honestly? Not really very much at all . Some tools make things easier, but most of the kits can be asembled with precious little:

A nice pair of pliers and diagonal wire cutters are key.

So is a decent sander.

A bunch of 2" spring clamps - $1 each at Home Depot - I used about 30 at once. (once).

A couple or four Irwin bar clamps were useful (12"?). A combination square is handy and makes things easy, as does a wood chisel, but they're not indispensible. You'll need a drill now and then..

Personally, I love the shinto rasp, but a sander can accomplish the same things. The japanese saw is awesome. but any decent handsaw will do... (there's precious little sawing).

Regarding epoxy, some of the yellow epoxy spreaders, and fillet tools make life easier, as do the pastry bags (all from CLC).

Personally I never used a plane in either boat I've built... a router was as wildly exotic as I got (I had to borrow one).

But that's just me...

P

With regards to clamps, it depends on if you want to clamp one side or two sides at a time.  I had enough to do one side, but that means four days to laminate both rub rails.  Since I'm trying to get my PMD done by the 4th, I bought 12 extra clamps at Harbor Freight (the $3 metal body F-style clamps, they're actually pretty decent), so I was able to clamp one layer during the evening and clamp the second layer the next morning so that my rubrails only took 24 hours.

The spring clamps are also very useful.  I've used the shinto rasp exclusively and also the $11 pull saw from HF.  I don't use the pastry bag or the pre-tape fillets methods.  I use a 2" wide plastic putty knife, radius the corners and goop it into the corners by hand, then use the yellow 3M style spreader to scrape up the extra.  It leaves a perfectly fine fillet that can then be smoothed a couple hours later with a gloved hand and denatured alcohol.  

Random orbital sander with dust collection.  I only used a hand plane for the scarf joints because I'm a plans builder.  Definitely a 1" chisel.  You can get by with a small router that handles 1/4" shank bits.  There's not much heavy duty routing.  The radii is more of an aesthetic choice on some parts.  I've used different radii for the rub rails, daggerboard slots, etc.  Just make sure that for the edges of the seats, your bearing has sufficient surface to roll against on your second pass (meaning the radius shouldn't be more than half the thickness of the part).

   Hate to break this to you,but there's not much of an excuse to buy toolss.im using the orbital sander less and less ,hand sanding works suprisingly well.one tool i use extensively is a belt sander and thats handy for lots of other projects too