For more information and to purchase online:

Seasons 1 & 2:
http://www.amazon.com/exec/obidos/ASIN/B0000ZMH8S/ref=nosim/happydaysonline3-20

Seasons 1 & 2 (Mill Creek):
http://www.amazon.com/exec/obidos/ASIN/B00I099JUK/ref=nosim/happydaysonline3-20

Season 3:
http://www.amazon.com/exec/obidos/ASIN/B000DZ854A/ref=nosim/happydaysonline3-20

Season 4:
http://www.amazon.com/exec/obidos/ASIN/B000FBH3WW/ref=nosim/happydaysonline3-20

Season 5:
http://www.amazon.com/exec/obidos/ASIN/B000MGTQ6Q/ref=nosim/happydaysonline3-20

The Complete Series:
http://www.amazon.com/exec/obidos/ASIN/B001DSNEM4/ref=nosim/happydaysonline3-20

Today, Amazon has the slim (crappy) packaging for $30 for all 5 seasons:

http://www.amazon.com/dp/B001DSNEM4/ref=asc_df_B001DSNEM41380420?smid=ATVPDKIKX0DER&tag=pg-1582-100-20&linkCode=asn&creative=395093&creativeASIN=B001DSNEM4

It's under $20 now. Wish I remembered my login email address. :D