Where would I go to find people who are willing to invest into my business or to invest in their business?

If I am looking for investors or people who would like to use my services or vice versa, where are the best places to go on the internet to find them?

My friend, I would advise you not using the internet for that. You will become highly misled by all the offers there. Your best bet would be to:
1. Prepare a business plan (the format for this you can search for in the internet=
2. Take your business plan and powerpoint presentation and offer to introduce it to local private investors whose door you have to go knock on... Dont go to public companies, but to actual private investors.... Private banks (Jpmorgan, Goldman Sachs and especially Citibank, can help you get in contact with some of their clients who are interested in investing in new ventures).

what u talk'in bout' willis?

If your looking for people to invest in your business, the best place to start are conventions, of course the convention must be relevant to what sort of business your running. If your product/service has potential, investors will most likely look into it. Something which is particularly important with investors and to increase your chances of success is a demonstration of your product/service.

'Carc CowBoy' has made some noteworthy points as well.

As for investing, I would recommend starting out small, perhaps contact a broker and just buy some shares :)

To answer the latter part of your question, use google to find conventions/brokers local to you, or contact financial institutions, like 'Carc Cowboy' has already stated.