Only few methods are available in online demo. You can find various methods in the SEMILAR package which is available here for download. In addition to sentence to sentence similarity methods, SEMILAR has many word to word similarity methods and document level similarity methods as well. You will also be able to use them in different configuration settings.
Please provide two sentences, select the similarity measure and then submit to get the score (in the range of 0 and 1). However, the scores distribution within this interval may vary from method to method