Pertaining to your questions:
1) the website where you can find available Low Cost/Low Medium Cost in Penang State for apply is http://erumah.penang.gov.my/ ;
However, the information publish there are just only those projects which have been available at time being, or meaning that the State Govt has forwarded the qualify purchaser list to the developers for the developer to send out Offer Letter). There are also those projects not available at the moment but the applicant might want to wait as the projects will be soon available. So it is good that you call 04-650 5138 (Office of YB Wong Hon Wai, State Exco for Housing) or Housing Dept 04-650 5392 to make some inquiries.
2. For application (Low Cost - Household Income less then RM2500; Low Medium Cost - household income between RM2500 to RM3500), you can go to Housing Dept counter located in Pejabat Pentadbiran Negeri Pulau Pinang (same as MPPP collection counter) at Komtar Level 3, ask for Borang Permohonan Untuk Membeli (PN1). Form available at RM1.00.
(Tips : It is important for you to fill up the project name or at least the location so that you have higher chance to be selected).
3. Anyway, I always advise people to "appeal" every 6 months to 1 year in order to keep their name in active list. The Appeal Form (Borang Rayuan) is in pink colour, purpose is for people to appeal those project of their choice. Form is available at free of cost.
4. When one has particulars change (household income, address, phone number), please do update with PN2.
5. FYI, factors/status of applicant that being considered include duration in waiting list, place of birth, marriage status, numbers of dependant, duration of stay in Penang, ex-serviceman, current dwelling status, reason of lost of current dwelling, occupation, and if there is a rejection to housing offer in the past. (Tips : Lower income doesn't make you stand better chance as long as you are still in the range. Applicant for low cost needs to consider the logic/feasibility of their household income against monthly housing loan instalment along with other living costs/expenses).
6. If you think you are not getting full pictures/info from the staff in the offices mentioned above, you can contact me @ firstname.lastname@example.org but you have to help me by writing in the email the problem of the service of these offices.