Who has the cheapest domain transfer/private WHOIS combination? I wish to hide the info for 2 undeveloped site names coming up for renewal.

You might want to take a look at www.domainsatcost.ca which provides their privacy service for free or www.registerfly.com which at times (during their promotions) provides it for free.

Registerfly has been charging $1/yr for privacy protection.
Namecheap provides the first year of Whoisguard free. After that it's $4.88/year, but you can get Whoisguard for two domains for the price of one.

Registerfly.com --> $0.99/year

Most of the time it is FREE with domain registration cause of their promotions.

some companies are running specials and offering them for free these days.
but its usually $1 - $9 for whoisguard these days

Beware of Registerfly. Aside from all of the complaints on this forum, the Better Business Bureau (http://www.trenton.bbb.org/nis/newsearch2.asp?ID=1&ComID=0221000010002016) says:this company has an unsatisfactory record with the Bureau due to unanswered complaint(s). Complaints processed concern service issues and credit or billing disputes....The Bureau has requested basic information from this company. The Bureau has not received a response.Since Registerfly is an Enom reseller, I hold this against Enom too.

I Had personal bad experience with Registerfly a few days ago. I emailed them asking about Protectfly (https://registerfly.com/protectfly/), which is their private whois service. Their webpage says "you can renew and transfer the name at any time(transfers require you restore your registrant info)." I wanted to know if that means my personal information will be made public during propagation if I transfer to a different registrar. No response.

RegisterFly is Icann accredited FYI

Having been with them for three years and having 6000+ names now they are excellent. At 1 million names now they are pretty solid

Yes, I see now. Must have been within the last year or two.

http://www.icann.org/registrars/accreditation-qualified-list.htmlRegisterFly.com, Inc. (United States)
http://www.registerfly.com
RegisterFly.com provides affordable and reliable domain name registration and web hosting services. Our extensive selection of various products and services is backed by 24/7 World class customer service via phone, live chat and email.

Tel: +1 973 736 2545
Email: sales@registerflysupport.comWorld class customer service? :rofl:

...edit...looks like they became ICANN accredited this month.

I don't know if it's still the case, but in the past to transfer a domain the new registrar has wanted to confirm the request by email to the whois-listed email address. Here is where differences in privacy protection services can show up. I'm not sure, but I think Registerfly's system is privacy enabled or disabled. Turn it off and your email address is accessible to the prospective new registrar, and also to harvestable by spammers.
Namecheap's whoisguard generates an address for you with a big series of numbers and letters. Email to that address will be forwarded to your email address they have on file. Spammers will never see that address, but spam will get forwarded. You can stop the spam by selecting option to create a new address. You can select or deselect periodic creation of new address. That can make a spam-harvested address useless before the spam-run is set up and transmitted.
Godaddy's Domains-by-proxy creates an address to display that has user selectable options to not forward (default), forward all, or spam-filter forwardings. Since the display address doesn't change, if you switch on forwarding option you might get much forwarded spam, although the spammers will never see the address it's forwarded to. Reselecting no forwarding should immediately stop the spam.

to transfer a domain the new registrar has wanted to confirm the request by email to the whois-listed email addressI wouldn't mind showing my email address in whois, especially if it's just for a few days, during a transfer. I wouldn't want to risk missing legitimate, non-spam emails by using Namecheap's whoisguard. I'd have my spam filter take care of the filtering and let all email be forwarded to me.

If your email address is already in the hands of the spammers, I guess it doesn't matter. If you have a spam-free email address, it takes very little exposure in the whois for the spammers to get it.
Namecheap's whoisguard should allow good forwarding if you deselect the feature to generate new addresses far enough in advance. I don't know exactly how far that has to be, as some whois databases take time to update.

Namecheap all the way !

Free whoisguard protection the first year.