Q:

Looking for stats/probability practice problems with data and solutions

I am looking for a self-study site on the web that will allow me to verify my understanding of some basic probability and stats concepts and operations. 
What I would like is a site with data and problems (along with the solutions) that I could use to practice my skills (such as regression methods/analysis, pairwise t-tests, computation and interpretation of confidence intervals, etc.).  I've seen workbooks like this, but the data is not available for me to import into R or Excel. 
Surely there must be a site like this on the internet, arranged by topics for study, but somehow I have not been able to find it.  Also, if anyone knows of a good workbook that comes with data (on CD or via web) I'd be interested in it too. 
I'll be using R and Excel - so pointers to these would be great too. 

A:

If you are interested in Statistical Machine Learning, which seems to be THE thing these days, Tibshirani, Hastie, and Friedman's book is an invaluable resource.  It is the latest edition and has a self contained website devoted to it. 

A:

The Statistics topic area on Wikiversity is worth a look.  It's got a long way to go before it's a comprehensive stand-alone syllabus, to be honest, but some of the Courses are more advanced than others, and when there's not much material as yet there are often links to free online resources. 

A:

I realise that this may not be what you are looking for, but R core and all packages come with data sets on which to practice the functionalities in each package.  Many of these data sets are quite famous, and often a link is given to the paper in which the data are described.  You could use these datasets in R and then after you finish your analysis look at what the authors of the paper did with the same data. 
That being said, its rare for there to be a right answer in any real data analysis problem, mostly one learns by realising that your techniques were not appropriate and re-iterating until one reaches some level of statisfaction.  Obviosuly this is a moving target though, as your skills increase an older dataset may yield new insights. 