I finally got around to building my own client from source (on Ubuntu) and the first thing I did was to add sound effects. I now hear a little pop whenever there's a transaction, and a chime when there's a new block.
It was easy, here's the diff for main.cpp, just 3 lines:
diff --git a/main.cpp b/main.cpp
index b7dfd9f..1196520 100644
@@ -4,6 +4,7 @@
@@ -2575,6 +2576,7 @@ bool ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
else if (strCommand == "tx")
@@ -2628,6 +2630,7 @@ bool ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
else if (strCommand == "block")
vRecv >> block;
For snd_tx.wav I used http://www.series-of-articles.com/sfx/snd/pop.wav
; for snd_blk.wav I used http://www.series-of-articles.com/sfx/snd/bell.wav
A quick hack, but entertaining and informative.