"Where can I get free ring tones for my T-mobile phone?"

Try Myxertones.com you will have to create an account but it it totally free and I have never gotten spam from them. You can also create your own mp3 ringtones from mp3s that you have stored on your computer.
Or you can go to PRP2’s site at wap.prp2.com on your cell’s browser. ( If you don’t have internet access on your phone you can get a plug in from firefox to view it on you desktop or laptop computer, then you can download then and transfer them to you phone with a data cable.
Also, if you have a bluetooth enabled phone and someone you know has a ringtone that you want and also has bluetooth, you can just beam it over to your phone. You will have to consult you phones users manual for instructions on how to do it, but it is another way to get free ringtones. :D

I have personally downloaded a large collection of ringtones and manually uploaded them to my phone using a transfer cable I bough on ebay. With bluetooth, you don't really even need the wire these days

Finding ringtones is generally the easy part, simply google Free Ringtones and you come up with a number of good hits, the hard part is figuring out the best way for you to get them on your phone.

http://cellphones.about.com/cs/originalringtones/

has some ring tones that you can put on a T-Mobile phone.

Getting them on your phone can be easy or tricky depending on the phone model you have. The following suggestions comes from http://cellphones.about.com/od/freeringtonesbycarrier/a/bc_t-mobile.htm

Free T-Mobile Ringtones Strategy #1: About.com's wap download system

Simply choose a compatible T-Mobile ringtone (go back to Step #1) and click on "Download it for free" then follow instructions. Enter your carrier and cell phone brands and you will get a number of suggestions on how to download that T-Mobile ringtone for free. Most of the time, it will include WAP download. From there, just follow instructions.

Free T-Mobile Ringtones Strategy #2: Infrared or Bluetooth

If your T-Mobile cell phone is equipped with either Bluetooth or Infrared and your PC or laptop is so-equipped, you can follow those easy steps to transfer ringtones for free:
# Choose a free T-Mobile ringtone (See Step #1)
# Instead of clicking "Download it for free", right-click the "Listen" link and select "Save As" to save that free ringtone to your computer hard drive
# Following your cell phone's owner's manual instructions, connect your computer to your T-Mobile cell phone using Bluetooth or Infrared
# Transfer your new free ringtone to your T-Mobile cell phone
# From your T-Mobile cell phone's menus, assign the newly transfered ringtone to your phone's ringtones (the technique will vary from phone to phone)
* If your T-Mobile cell phone allows it, you can also do that with any mp3 or compatible music file.

Free T-Mobile Ringtones Strategy #3: Using a Memory Card

Many cell phones feature a small memory card reader. Maybe your T-Mobile cell phone does. And if your computer also has a card reader (most laptops sold after 2004 do), then you may simply use a memory card to transfer free ringtones to your T-Mobile cell phone. Here is how:
# Choose a free T-Mobile ringtone (See Step #1)
# Don't click "Download it" but right-click the "Listen" link and select "Save As" to save it to your computer
# Transfer the ringtone to your memory card
# Insert the memory card in your T-Mobile cell phone
# Transfer your new free ringtone to your T-Mobile cell phone's memory
# Assign your newly transfered T-Mobile ringtone to your cell phone's ringtones (the technique will vary from phone to phone)