I'm new to Arduino. Does anyone have suggestions on how to manipulate my Arduino remotely? Specifically through the internet? Any services or SW?
Since the Arduino can communicate via a serial link, all you need is a programming language that can a) talk to a serial port, and b) be used for web application development.
That opens the possibility to just about every programming language, but the easiest to work with will probably be PHP, Perl, or Python; others include C/C++, Ruby, Java...
You basically set things up to have the web server run the code you develop in your language (either interpreted in the case of PHP, or the compiled version for say, C/C++), which would (simply put) generate the web form for control, and parse the inputs from the web control and output the data in the format needed to the serial port, where the Arduino would interpret that and act upon it as needed (and perhaps send data back which the application could then parse and display on refresh, or via some other method).
That's the basics, anyhow...
