Not for all problems but for some technical ones I use lovely curated awesome lists.
https://github.com/sindresorhus/awesome is a good starting point.
http://alternativeto.net/ is pretty good. You need to know one tool in the area you are looking for, but if you do it gives a good list of alternatives.
Slant[0] and StackShare[1] are probably your best bets. The former is better for desktop applications or utilties, the latter is better for frameworks and the like.
If you're looking for a specific niche, Product Hunt has a ton of curated lists that tend toward marketing/design. GitHub is probably a better source for curated lists which focus on things developers would find useful.
[0] https://slant.co
[1] https://stackshare.io