Another source of RFPs is the RFP site. The best of the RFP sites, in my experience, is The RFP Database, and I like it because it gives you access to a wide variety of RFP types.
The RFPDB is a pay-per-bid RFP site that we find about 3-5 great RFPs on each month. The site is actually a co-op where agencies share RFPs with one another. There’s lots of categories, so find the one that makes sense for the work you’d like to do.
Just know that you’ll usually need to go through a few RFPs to find a good one on these sites. There’s a lot of long, overly-bureaucratic type documents on RFP sites in general. So be prepared to throw out some of the RFPs you pay for before you find something good.
I always pick the short, reasonable, high-budget RFPs when I’m curating my website design RFP newsletter.
The good thing is there isn’t as much manual labor required when searching through these sites. You’ll typically just need to pay anywhere between $2-10 per RFP.