I recently installed steam and TF2 via PlayOnLinux, and I need to find the steam folder, on windows it is on program files. Any ideas on where could i find it?? thanks
Inside your Home Folder there's a Folder called PlayOnLinux virtual drives, click it.
Alternatively open your Home Folder, press Control+h and you'll see this:
Click it, then go to the folder wineprefix inside and then to the default inside of it.
EDIT: I didn't notice you were referring to running Steam in Wine. But just to point it out, Steam is now available for Linux natively(without Wine) and TF2 is Linux supported as well.
The Steam folder is located in:
Keep in mind that if you want to move the Steam folder you must copy it to a location with an EXT3/4 partition format(Ubuntu won't launch Steam from a FAT or NTFS partition without modification to certain system files). You then must Right-Click on the Steam folder and click "Make Link". Copy the link to the Home Folder and then rename it to "Steam". The Steam folder should now be detected in it's new location.