As I run a Investment Fund, I have shares in almost all of the trust able companies on GLBSE.
I recommend TyGrr the guy that owns the mining company is very nice, easy to contact and listens to the share holders wishes, he has photographs to back his mining rigs up they do exist, he has also given out his identity. So TyGrr I recommend as they seem to be a safe bet and they are run in a professional manor, they have a nice dividend of about 0.023 BTC per share a week.
MergedMining I also recommend, run in a nice and professional way so far. Everything is running smooth and nice regular dividends. The guy running it seems nice as well. The prices for the shares has been steadily increasing so it would be a good investment for both short term and long term investment.
In general I like all the LIF shares, LIF.B closed recently which has pushed down the prices of the other shares as well as created a bit of mistrust, but I believe that the LIF companies are run in a professional manner and that are a good long term investment. They don't have that high dividends but the share prices have been on a steady increase over time. If you want a short term investment I would say go with LIF.M as they have a good dividend, if you want a long term investment go with LIF and LIF.A
Those are probably my favorites atm, if you want any help or advice just ask
A tip is to always check for information about the companies before investing, as there are still some old companies that no longer exist on GLBSE as well as some scam companies that will run away with your money. Make sure all the companies you invest in exist and seems reliable
Best of luck with your investments