Are there any resources that analyze the purpose or goal or the major viruses/malware out in the wild today? For example, what percentage are used to construct botnets (for DDoS or something else)? For sending spam? For keylogging and collecting passwords or financial information? For destroying information on the machine? etc.
It's unlikely to find open resources that will give you this information in the format you are looking for.
However, you may be able to mine that information out of annual reports published by major Antivirus vendors like Microsoft, Symantec, etc. As an example, Microsoft publishes all its findings in its Security Intelligence Reports every 6 months which is a pretty comprehensive report of all malwares discovered in the wild.
In my experience as a server administrator for over a decade, the most common reason malware strikes is to send out phishing emails to gain financial information (in turn, selling this information to criminals is quite profitable).
As mentioned before, most security and antivirus software firms release their own reports and statistics but it may be skewed as a marketing tool to scare consumers into using their products and/or services. However, you can glean some information from these reports to give you some idea.