Hey look, I'm useful every now and then : )
On "legally carry", it's different in every state.
mynameisfred you're still in CA, right? I took a quick browse through their laws and (obligatory) I'm neither a lawyer nor reading super closely, but it looks like folding knives are legal (carried closed) either open or concealed but fixed blade knives must be carried openly. I didn't see a blade length law but many states have them.
Also keep in mind that effectively every knife is illegal if carried with intent primarily as a weapon. So, always remember that you're carrying a tool, not a weapon... though it could serve that purpose if it was required to.
With that out of the way, on to the fun bits!
With one (very important) caveat, I can't recommend the Mora Companion HD enough (http://www.amazon.com/Morakniv-Companion-Carbon-Military-4-1-Inch/dp/B009NZVZ3E/). It's cheap, it's thick/strong, it's high carbon steel (caveat to follow), it gets razor sharp, it stays sharp, you can abuse the crap out of it, and it's a scandinavian grind so it's easy for even the most novice person to sharpen correctly and efficiently. The absolute only drawback is that, because it's a high carbon steel blade, it will rust easily. You can look at that two ways -
1) you have to take extra precaution to ensure it is always dried and proper lubed (like you should) or
2) it's crazy cheap for as good as it is and you can buy another if you screw it up too badly.
It is only a 3/4 tang blade, but it would take some insane abuse to get it to the point a 3/4 would fail and a full tang wouldn't. I've chopped through ~4inch thick branches with mine, batoning it with another stick.
O, and to explain 3/4 vs full tang - the tang is the non-blade part of the knife that goes into the handle. A "full tang" means that the piece of steel that makes up the blade runs the entire length of the handle as well - one piece. A 3/4 tang means that the steel runs 3/4ths of the way into the handle, so it's not quite as strong as a full tang.
Further explanation of a high carbon blade : You have a choice in metals and the primary varying factor is the amount of carbon. The more carbon in the blade, the harder it is (therefore the sharper it gets/stays) but that makes it more susceptible to rust and chipping/breaking rather than bending. That is, a lower carbon blade is less likely to rust/break but it will not get/stay as sharp and may bend instead of breaking. Whereas a high carbon blade will get/stay sharper but will rust easier and may break (chip) rather than folding the blade.
I have a lot of both kinds, but I really love my high carbon blades because they get and stay so amazingly sharp. Also, I usually force a patina and don't worry too much about surface oxidation on a $15 blade... though it does hurt my soul when it happens.
If you're intimidated by the high carbon blade, but want a lot of the superior properties of it, you might consider a blade made of AUS8 or CrMoV13. Both get quite sharp and are less susceptible to rust. I have a few of each and I really like them (my current every-day-carry folder is CrMoV13)
You typically don't see high carbon blades in folding knives, but it does happen.
EDIT : Blade types (shapes) - there are tons of different blade shapes but only a handful that are common and popular. You're pretty much looking at clip point, drop point, tanto, or sheepsfoot... and wharncliffe has been getting more popular lately. There's a lot of good info here :
www.knife-depot.com/knife-information-112.html so I won't rehash it.
Second to the blade shape is the edge - your three options are a standard edge, a fully serrated edge (rare), or a partially serrated edge. Personally, I do not like blades that have any serration. I like to have the entire length of the blade as a straight edge and equally sharp/usable. But, if you were expecting to be cutting a lot of cordage or rope that isn't tiny (think jute cordage), a serrated edge might be called for because you can saw through the material more readily than repeatedly slicing at it.
END EDITSo, let's talk folding knives. The upside? They're smaller/lighter and less widely restricted. The downside? They're going to be weaker so you probably don't want to try to chop down a tree with one.
So, brands? I'm a pretty big fan of Mora, CRKT, and Kershaw. Mora only makes fixed blades I believe, I linked the Companion HD above. CRKT is kind of a "cheapo" brand, but most of what I have of theirs is surprisingly good for the price. Kershaw makes good stuff, and has a great warranty, but I only buy them on sale from the deal-a-day sites like woot. If you can find a Kershaw for $15 or less, always buy it... that's my rule : )
Here's a few of the blades that have carried over the past few years and I do like all of them. They are varied in their intended purposes :
www.amazon.com/Kershaw-1028OR-Antelope-Hunter-Knife/dp/B001TE7CUMwww.amazon.com/Morakniv-Companion-Carbon-Military-4-1-Inch/dp/B009NZVZ3E/www.amazon.com/Kershaw-3830-Injection-Pocket-Knife/dp/B00AU6NV5U/www.amazon.com/Columbia-River-Knife-Tool-6450S/dp/B001BG8PP4www.thetruthaboutknives.com/2013/05/knife-review-crkt-tuition/www.amazon.com/Columbia-River-Knife-2010-Dragon/dp/B000M3SYR6/www.amazon.com/Kershaw-8100-Funxion-EMT-SpeedSafe/dp/B00KYR1UGM/www.amazon.com/Kershaw-Blade-Trader-Polymer-Handle/dp/B000WAFQH0 (only for butchering game)
www.knifecenter.com/item/UC2867/United-Cutlery-Honshu-Large-Push-Dagger-4-inch-Satin-Blade-Leather-SheathThat UC push dagger won't get sharp but it isn't designed to be sharp, it's designed to be strong at the point and it does accomplish that.
Did I miss anything? I discussed steel types (to a degree), fixed vs folders, legalities, brands....
Post back if you have any questions. With any luck I'll be forging my own blades in the next few months, but more on that later : )
EDIT : Fixed some typos. Also, I probably should've said that any knife is better than no knife. Find something you like that you can afford, learn how to use and care for it, and explore from there. Personally, I'd rather have five $20 blades than one $100 blade, but I'm cheap so your choices may vary.
EDIT x2 : I didn't really discuss specialty blades. Any of these will gut a fish, but it would be pretty tough to filet with any of them because I was favoring thick/strong blades. Don't forget that there are many blade styles and the well established types were developed for a reason, for a special purpose.
