I think .info and .biz have a good future. They are generally the next best top level domains after .com, .net, .org. Once those three are taken then the info and biz are next best if you want to promote worldwide, and they are usually shown in the results anywhere you reg domains, so they are visible. Or, you can also use your own country tld.
The value of .info is certainly going to rise in the near future there's no doubt about it, while the value of .biz will rise as the availability of other TLDs for commercial purposes is declining but it may take a few more years
For information sites .info is obviously the one, there have been multiple $x,xxx sales although things seem to have dried up of late.
The .biz extension I do not see, for a start their is a .bz extension (Belize) and with the correct marketing that could take a lot of any potential traffic from the .biz suffix.
I think if anyone of you owns a lot of .biz and .info...domains... you should put some of them to use as developed websites. A developed website beats out any parking plan anyday...however the reason I'm saying this is ...for example...
I read somewhere that only about 30% of .biz tlds are developed as proper websites as compared to about 80% of .com tld and also high figures for .net tld.
The current view is that .biz is a less desirable .tld and one of the reasons is people think its a speculative tld....and not mainstream... so there you go. Most people may not know it exists.
I personally don't like the idea of using various cctlds to make up words, like .es, .is, .se. I'd rather own those domains with good words in the language of the country. I mean, what is the market for a chopped up word in an extension most people aren't familiar with? Sure, there's a few exceptions but far from widespread use. If you are regging names like that I would say it's highly speculative.