Android 3.0 builds on the previous versions, so you'll need to learn Java, a development environment (many use Eclipse, though I prefer IntelliJ IDEA), the platform itself, and the 3.0 extensions. Here are some resources that may help:
My top tip is to get Mark Murphy's excellent ebooks on Android. Mark is a prolific Android trainer and author and has over 70k on Stackoverflow. His v3.5 ebook release includes coverage of v3.0 Honeycomb. For $40 you can't go wrong, and it's fully up to date.
Reto Meier of Google also has an Android development book, in Kindle or paper format which is required reading in my view. Reto has an excellent blog post on Android 3.0 UI fragments. Do be aware fragments and tablets in the context of v3.0 are not covered until the next version is published.
Java is very similar to C#, but different (e.g. no properties, a real shame). See this wikipedia article for a list of the differences.
The primary resource will be the android developer site, so be sure to look in the resources section for tutorials and samples etc.
I've yet to read it (purchased tho) but hear good things about Android Development for Dummies though that was published before Android 3.0, so fragments etc won't be in it.
If you like to watch videos there are some talks here from Google IO 2010 that cover Android, though none on Honeycomb, that will come after Google IO 2011.
Android is a big platform, you won't pick it up in a weekend, so allow some time, and focus on what you need to learn to reach a specific goal. Note that to do Android 3.0 development and make use of the new UI, you need to use Fragments, and the Action Bar. Both are included in the new 3.0 SDK (SDK platform release 11).
