asp is a cheap and dirty way of getting things done. it is reasonably fast in terms of scripting languages (server side). amny sites use this b/c of those reasons. it is reasonably fast.
cold fusion, depending on the tests, is slower. and it sucks to write in. but there are plenty of places using it, which means they need coders that use it.
php - fast as hell, allows you to do a lot, free, great to program in (although it might seem hard if you are new to programming... I personally love it - I think Warik does too

) - it is the fastest of all of them. it will run on linux/unix or win - but I personally prefer it on linux.
perl via cgi - this is my least favorite reason to use perl. perl rocks, but I don't like cgi programming.
and it can be pretty damn slow.
jsp - REALLY FUCKING SLOW - but on any platform. it is by far the slowest, and it is a pain in the ass to write... well, that's not true. the J2EE standard is the part that is a pain in the ass.
I'm sure there's more, but those are just off the top of my head.
linux is good - but as r00+ has pointed out many times, just b/c you install it and get it up running, doesn't make you an expert. there is still much to do.
but if you like computers, it is a nice way to play with them and learn some stuff along the way.
I currently program in java at work, access that via jsps, and hate every moment of it (there is just so much and people all have their own coding styles and it fucks things up....).
at home I mostly program in perl b/c you can do so much so fast, in so few lines. but it isn't very good for large scale things, like cryptography or games - that is where either C++ or C comes in.
that is probably where I'm weakest simply due to the time between projects I do with it.
there is plenty out there, and everyone has their own preferences. but I'm right.
hee hee.