Want to try out Linux, what do?

First and foremost you want to find a shell reference. No matter how good of a guide you find on Linux, you'll want to be able to look up individual commands and how they work. This is the official GNU Bash Reference Manual, so it should be fairly complete.

As a programmer, you will soon like to use the advanced bash scripting guide.

Also get familiar with man pages. Most commands should have a manual, accessible through 'man commandname' in the terminal.

There's also a wiki on all things Ubuntu specific.

Of course Ask Ubuntu (au) and Unix & Linux (ul) from this StackExchange-stack are glad to invite you if you with your questions. :)

Here's a short list to get you started:

• bash
• history
• grep
• find
• cat
• less
• tail
• screen
• sed
• awk
• curl

Try using the man command on any of the above, as well as the info-command, plus google, of course:

man grep
# maybe first:
man man
info 
# usage for example:
info coreutils date invocation

Anyway, the other answers are just as good, I just know that I use the above commands every day, all day long.

Have fun!

A great place to learn about this stuff is on IRC:

  FreeNode (this network is popular among many developers)
  http://www.freenode.net/

You'll need an IRC client (there are many to choose from), or you can use the web-based chat at http://webchat.freenode.net/ if you prefer. The #Linux and #Ubuntu channels are very popular there, and would probably be really good places to get started -- you can learn a lot just from watching what the thousands of people ask about on this helpful network.

SuperUser.com has a Chat system as well, which I believe has a pretty busy Ubuntu channel (they call them "rooms" rather than "channels").

Also, take a look at the long list of [mostly] well-known Linux distributions, and at least try a few of them before getting your heart set on one in particular:

  Resources - Operating Systems - Linux distributions
  http://www.lumbercartel.ca/resources/os/linux.pl

Each distribution of Linux has its advantages, and also many differences (some are more noticeable than others). Depending on your needs, one distribution that meets all your criteria may not be suitable for someone else. (It sure is nice to have all these choices!)