Is there a Project Euler-alike for machine learning? I found Project Euler http://projecteuler.net/ to be incredibly useful in learning programming languages. Is there a similar site for Machine Learning?
I did see http://www.kaggle.com/, but it is not nearly as accessible to beginners as Project Euler.
 A: UCI is well-known in the machine learning community for their repository if datasets. Many journal articles include results of their techniques on some UCI datasets, so you can try yourself and see how you do.
A: How about: http://www.ml-class.org/? It has good introduction and some programming excersises. AFAIK Euler has much more sophisticated examples, but ml-class is still a good beginning.
As it was pointed in the comments this course has next edition: http://jan2012.ml-class.org/#
A: Though the stakes are higher than for Project Euler, as you've pointed out, Kaggle is an excellent source of data for use in your own experiments.  Many of their contests require you to be signed in to access the datasets (for legal agreements and so forth), but if you don't actually finish an entry, there's no penalty that I know of.  
That being said, if you look for data sets that are specific to testing statistics procedures, like the ones at Princeton, you can test the data on different network architectures and compare it to plain regression, etc. as a benchmark.
See also here for a comprehensive list, which includes all of the Google natural language processing data.
So, Project Euler provides a great service with specific problems, but in the case of machine learning, you can use existing datasets with an architecture of your creation and compare the "answers" to conclusions that are presented online or in research papers.
