iTunes blew my mind. I spent 3 days in college getting all my bootlegged mp3s set up. iTunes was so powerful and intuitive compared to everything else I was aware of at the time. It got me thinking about why some things are great while other things suck.
Frontpage 2000. When I was a youngerster and playing with what I had on my computer, this program opened a lot to me. I loved being able to switch back and forth between the coded mode and the viewable mode. I did learn some bad practices at first... the <br> tag was new to me later as I'd copied FrontPage's insistence on <p>nbsp;</p> instead, for instance. But it was what set me off to look at anything relating to hacking.. ;)
Netscape 6. It sucks as we see it now, but the integrated suite was so much nicer than the older versions of Netscape and the AOL-based thing I'd used. The mail client was phenominal to me, having used Outlook before, the web browser feeled so much nicer and more modern, and so on.
SuSE Linux 9.3. The first Linux distro that became my main OS instead of just a plaything. It perfectly supported all of my desktop's hardware and made me fall in love with Linux and especially KDE 3.x.
Amarok. This was the first media player that I really loved. Unfortunately it's been messed up badly with the release of KDE 4 in my opinion.. I've yet to try the backports. But after playing with stuff like Musicmatch and Media Player on Windows and then JuK and the like on Linux, Amarok seemed just incredible.
2) Usenet, Unix, VMS & Slirp (http://slirp.sourceforge.net/). I got to university and didn't know where to start
2) Doom. OMFG
3) Eclipse. The first time I saw the "Extract Method" refactoring I was speechless.
4) Google desktop search. Back when I had to use Outlook this let me actually find my email messages.
5) Dropbox. Been mentioned before, but it really did impress me that much.
We also had Microleague Baseball, which I wish I could find now it would be amazing. That game was awesome, it had custom speech capability and everything. EA Sports could learn a thing or three from them.
The first time I used this program, I was amazed. I had just started coding and here was a WYSIWG editor for data driven pages.
The program was buggy as hell and it was almost like learning another language the way I had to learn all the quirks of this program. But it gave me my start and I probably wouldn't have learned to code better if it had created halfway decent code.
I've been using notepad for this kind of thing previously because I just want a simple think of it / dump it / get back to it later type catchall. This suits the function perfectly.
Slightly off topic: MidWinter. Massive believable world, multiple forms of transport. This game sticks in my memory.
(Eclipse has managed to win me over for Java development now.)
What more could you want out of software?