For those keen to use R but yet need a quick start to solve some immediate data-mining problems, you can use Rattle.
From the Rattle website:
Rattle is a popular GUI for data mining using R. It presents statistical and visual summaries of data, transforms data so that it can be readily modelled, builds both unsupervised and supervised machine learning models from the data, presents the performance of models graphically, and scores new datasets for deployment into production. A key features is that all of your interactions through the graphical user interface are captured as an R script that can be readily executed in R independently of the Rattle interface. Use it as a tool to learn and develop your skills in R and then to build your initial models in Rattle to then be tuned in R which provides considerably more powerful options.