Well, let me see:

- Google: I still remember when the normal web search was the only option and it was still beta, but the quality of the search results was just so incredibly much better then everything else at that time

- Wikipedia: I'm still amazed about how well it works, considering that every Joe sixpack from around the world could write crap into a random article, but still, most of them are very high quality, and quite understandable, too

- Vector graphics: My first encounter with vector graphics were PDF files that had embedded vector graphics, and they were looking great even at the highest zoom level. I was very impressed ...

- Google earth: When we installed it first on the new laptop of a friend of mine, we were simply amazed about how fast and smoothly one can zoom into and out of the area, and how high resolution the Frankfurt (germany) airport is (we live not very far from it, so it was the first location we came up with after our home villages).

- X forwarding: The local display of the GUI of a program running far away, without having to do a complicated setup and without quality loss (the program windows loop perfectly clear and crisp). Holy cow was I impressed!

- GPS: Getting your location and speed, anywhere on earth, with a cheap handheld receiver, is just way cool.

- IMDB.com: The ability to read about each and any flick that ever run anwhere on earth, no matter how short, cheaply made and unknown. I never would have thought there were this many movies made every year, and how old the oldest ones are. Way cool!

- Unreal (the original game, probably from something like 1998). I remember how impressed I was about the quality of the visuals and sound, even on the cheap, midrange hardware that I had. It was the first time I found the graphics of a game level really that great that I simply forgot any gameplay and just wandered around the level, enjoying the great view.

- USB sticks: 128 MB of space on a stick that weights about 19 grams and is not much thicker than an ordinary text marker? And that works on any computer, now matter if Windows, Linux or Mac OS (X)? And that is actually quite cheap? Whow!

- A tool called "PE Explorer": The ability to graphically edit the user interface of many compiled windows executables is really cool. I never thought this were possible.

- Eclipse (for Java and PHP development): It's impressive to see how much more effective and faster you can be with great tools.

- Live Linux CDs/DVDs: You can start a complete operating system directly from a CD and you got THIS MANY programs that just work right away without any preparation? Whow!

- Finding out how incredibly old many ideas and concepts in mathematics are: Impressive, how detailed they thought and wrote about stuff that is both well known and really relevant some (sometimes many) centuries later!