This a pay for site but they have a huge community and vast collections. New collections are being added every day. They provide excellent support You may find that your local library has a free access to this site set up on their computers.
However, having said that, I found that after a while I wanted to be able to research from home and took out a basic membership with ancestry. After a couple of years, having found the membership to be so good, I upgraded to a full membership which gave me access to all of their collections. For a hobby, I found it an expense that I was happy to pay.
They have a member connect feature and I landed up making contact with relatives that our family had lost contact with over the years.

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You will need the geneology software, family tree maker. This application is now available for Macs.

This is a pay per view site, also with a huge community and vast collections. They do offer a 14 day free trial. If not wishing to take out a membership, you can search the site and have the option to buy credits which will allow you to view any results that you find.
I landed up taking out a membership with this site as well as ancestry, as there were some collections that are held by findmy past which aren't held anywhere else.
The pay per view sites (although the idea of having to pay is daunting) become very worthwhile as most of your initial research is centred within one site. It can save you hours of research overall. The military collection is the best that I've found and well worth the membership or payment of credits for this feature.

This site seems to relatively affordable with the annual subscription being 30 pounds. You have to register but there seems to be quite a lot of useful information contained on the site. Like Find My Past, there is also the ability to search for free but then pay to view the individual item. They do have a free section for searching the GRO Overseas records. It is worth a look

I found this site quite difficult to navigate. However, if you read the instructions carefully and search dilligently, there is a wealth of government information to be found on this site. Payment is by credit card and the document is ready to download immediately.
I have downloaded some wills and have been well pleased.

This is a huge site with world wide collections. They will give you an initial 3 day trial so that you can test out the capabilities of their searches.
Search Historical Newspapers

Family Link will give you a free 3 day trial. They have extensive USA collections and are adding to their UK Collection which is already quite extensive.

This is a relatively new site and their goal is to become one of the most popular. They have a broad coverage in the US and United Kingdom. They also provide access to smaller colections of international records, primarily from Europe and Canada. They are adding millions of records each month and working hard to expand their internation collections.
Click to visit site and select the country of interest from the dropdown box