Well, I recommend a hub motor since it's a lot easier to install and often has less problems long term.
These are some of the websites people usually buy hub motors from
ebikes.ca (canada)
hightekbikes.com
e-bikekit.com
itselectric.ca (canada and have a US Store, too)
cycle9.com
ampedbikes.com
A lot of people like ampedbikes.com . They have a good motor. I think they use a nine continent hub motor which is a good quality motor. I think e-bikekit.com also uses a nine continent motor. Ebikes.ca also sells nine continent motors. I think ampedbikes.com , e-bikekit.com, and hightekbikes.com are probably the best value. There hub motors are pretty respectable and most people prefer the nine continent over the chinese brands. As for batteries, lithium is the best way to go. Lithium is one of those batteries where if you know what you are doing and willing to do some research, you can save a little bit of money. I saved about $200 by choosing a lithium battery that required a little more maintenance on my part. Not everyone has the time or patience though. Also, it depends on how far you want to go. There's also NICD and NIMH batteries. You can look through some of the other battery threads on this forum to see about lithium batteries. I don't think you will be very happy going with lead acid batteries and I don't think lead acid are a good buy anymore because you can get lithium and NICD for just about $100 more.