JAVA
Well, I think JAVA is one of the most seductive concept in languages history. But i dont like it that much actually JAVA or actual browsers are too "buggy" for supporting JAVA applets correctly

Applet I made

Raising island
Psyko stuff

Other nice applets

Great Web chat applet
IRC on the web
others ones

JAVASCRIPT
JS is really cool, HTML was getting frustrating , now JS allows quiet everything.
But I have a few trouble w/ it : click on the TOOLS icon and then EXIT ... yea this security violation drive me mad. (Also called 'DataTainting' for those who can understand !)
And another annoying stuff : How to open a document into the original browser window from a window you have created (ie: click on EXIT)

ACTIVE X
This MicroSoft technology sounds VERY interessing too... BUT will I encourage the *monopoly* of the net for Mr Billy Gate ? NO ! Why ? because MS decided that it wasn't "Interessing" to devollop Active X on Unix machines (or even worse : non IE browsers).
Ideas yesterday / Mistakes today / Problems tomorrow

UNIX SHELL
One of the most intiutive language :-)

C
When nightmares become standards