A support package is a file built by a Solr installation that consists of configs, logs, and other pertinent information that can be helpful when help is needed to solve a problem.
Since version X.X, Solr has included a script for gathering support information and packaging it into a single file. This page describes what to do with this information once you have created it.
Creating a package
Chances are that you will have already done this before you get to this page, but if you haven't, here's what to do:
Uploading the package
The Apache foundation and the Apache Solr project do not have any dedicated resources on the Internet for support packages. You will need to either provide your own hosting or use one of the many public file-hosting services that exist. Some examples of publicly-accessible resources for hosting files:
There are many other services besides the ones that have been listed here. These services allow users who have free accounts to upload files and then make those files available to anyone with a URL. They do have limits on the amount of data that you can host at any one time.
Here's a wikipedia page comparing many different file-hosting services.
Once you have a support package that you have uploaded somewhere and have obtained a URL so others can download the package, you can use that information to try and obtain help. There are IRC Channels and mailing lists for Solr. Please try to ask good questions when using these resources.