WEP is about as secure as a fishnet condom. WPA is another matter entirely, and the recently introduced WPA2 with AES is supposed to be very secure.
However, as tolien mentioned, it really is only as secure as the monkey that sets it all up. It's no use having WPA2 with AES etc etc, when the key is something like "password".
A strong key (consisting of caps, small letters, numbers and symbols all together) should be much more challenging to a casual intruder.
PS. Hiding the SSID will only deter the most casual browser - most utilities show up the networks even without SSID broadcast. Same with MAC filtering - MAC is very easy to spoof so you will again only deter a very novice attempt.
In short: A minimum of WPA with a strong key seems to be okay for general use, so far.