iBook G3 won't connect to wifi

Which operating system version is installed?

For your information, here are the requirements for WPA:

AirPort Card: When You Can Join a WPA Network - Apple Support

As indicated by Tesserax, a USB wireless adapter could be one alternative, thus making it possible to use WPA2 security. However, please note that the maximum speed will be limited because of the USB 1.1 ports (in a late 2001 iBook G3). In addition to this, a USB adapter would need special drivers compatible with the installed operating system. There are only a few devices for Mac OS 10.4, and even fewer for 10.3.

Yet another option for WPA2 could be a wireless Ethernet bridge, such as the AirPort Express already mentioned by Bob Timmons. If you wish to use a web-based user interface for the configuration, there are third-party devices (like the Netgear WNCE2001). Some Wi-Fi range extenders with an Ethernet port (such as the TP-Link RE200) have similar bridge capabilities.

Most likely, the level of wireless security that the Wi-Fi network is using is not supported by your G3 iBook. One quick way to verify this is to temporarily remove any wireless encryption and see if the iBook can now connect.

It just won't connect. I've tried everything. It works when I use an Ethernet cable, but that's it.

What exactly by "I've tried everything" did you do to get it to work?

The G3 is only capable of connecting to an 802.11b wireless network. If you have a 15+ year old wireless router that is 802.11b only.....the G3 will likely connect if the wireless security is disabled.

The G3 might "see" so called "compatible" networks using "g", or "n" wireless, but it will never be able to connect to them, in my opinion, based on past experience.

If you need to use the iBook in a remote location, and cannot connect the iBook directly to your router using an Ethernet cable, then your options are to use an AirPort Express to "join" the wireless network and then connect a short Ethernet cable from the AirPort Express to the iBook.

Or.....use a pair of Ethernet over Powerline adapters to send the signal over the existing AC powerlines. One adapter will be located near the main router and the other adapter will be located where you want to use the iBook.

Putting a $ in front of the password, replacing the AirPort card, resetting the router, connecting to open wifi- none of it works.

Using a "$" sign would be related to the old WEP version of wireless security. Neither WPA or WPA2 would require this. Depending on the exact model of the AirPort Card, it may not support anything but 40-bit WEP. Revision 2 of this card supported both 40- & 128-bit WEP, but also WPA ... but not WPA2. Any card with a serial number ending in G3G would be a revision 1.

Also, as Bob has mentioned, this card is only capable of accessing 802.11b wireless networks. Most open Wi-Fi networks today use either 802.11g or 802.11n and may not be configured to be backwards compatible for 802.11b.

Even with an Ethernet cable, I can barely do anything.

Sorry, but I'm not sure what you mean by this. Connecting by Ethernet should provide your iBook with network connectivity, to its full potential, albeit at a reduced speed since the iBook only has a 10/100 Mbps Ethernet port. Again, not sure what you were expecting for a 15+ year old device.

One potential option would be to acquire a USB wireless adapter. I suggest that you contact a vendor, like Other World Computing (OWC), to see if they have something that may work with your iBook.