Simply search for, in quotes: "better than _keyword_"
Some example results:
Results 1 - 100 of about 550 English pages for " better than WinAmp".
Results 1 - 57 of 57 English pages for " better than mIRC".
Results 1 - 100 of about 17,500 English pages for " better than Digg". (Wow. Poor Digg.)
The results will almost always lead you to discovering alternatives to whatever it is you're searching for. Using the same concept, you can use this trick to discover new music or movies. For example, " reminds me of _someband_" or "sounds like _someband_" will pull up artists people have thought sounded similar to the one you typed in. This is also a great way to find good, no-name musicians you'd probably never know of otherwise.
Results 1 - 88 of 88 English pages for " reminds me of Metallica".
Results 1 - 36 of 36 English pages for " similar to Garden State".
Results 1 - 66 of 66 English pages for " sounds like The Shins".
Just get creative and you'll, without a doubt, find cool new stuff you probably never knew existed.