Checking the spelling of Tamil words (or any language like Hindi or Bengali or Telugu for which there are no good/easily accessible dictionaries are available) can be done using Google search.
I was just posting a pseudo-poem to my Tamil blog and I didn't know how I should spell one word correctly. It could either be spelled as சருக்கல் or சறுக்கல். In this time and age we don't have a lot of people who can answer such questions. So I ended up asking Google. I did a Google search for both words.
One spelling has 2,720 occurrences on the Web while the other has 40,300 occurrences. It's likely that the frequently appearing spelling is the correct one too. Well, it's not guaranteed to be correct; but this trick works for most, if not all, practical purposes.