I recently went into my local Ralphs (aka Kroger) to buy eBay Gift Cards with double rewards:
http://www.kroger.com/in_store/fuel/Pages/default.aspx

I buy these cards with my rewards credit card which gives me back 1% (but some people have 2% cards like Fidelity, Schwab, or PerkStreet. AmEx Accelerated Rewards is 1.25%).

Then I go to BigCrumbs which directs me to eBay

Then I go to Upromise which leads me to eBay:
http://shop.upromise.com/mall/merchant/ebay

I get eBay Bucks back and maybe 2x if I buy from a TSR or Bill Me Later that is eligible

Let’s see:

2% Kroger/Ralphs
1%-2% rewards credit card
     36% of seller FVF paid back
2% Upromise
2% eBay Bucks (or 4% if you buy from a 2x seller)

So, you end up with 7% and above in discounts in various forms.

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Kroger requires you to buy $250 worth of gift cards to meet their quarterly minimum of 500 points to get a payout of $5.

Rewards credit card usually needs 2500 points before you can redeem for full value.

The BigCrumbs pays out monthly via Paypal.

Upromise is for college savings (529)

2% eBay Bucks is paid out quarterly, and requires Paypal, with a max back of $500 per calendar year.