Please add your FF3 whatevers!
AwesomeBar
By default, FF3 gives you 12 lines of Awesome. If you'd like to adjust it, type about:config in your address bar. Insert browser.urlbar.maxRichResults in the search bar. Double click the entry and change 12 to whatever you like. (To disable it altogether, use -1, not 0) Source with pics.
Awesome Bar -> AutoComplete. (IE and Safari behavior) Type about:config in your address bar. Insert browser.urlbar.autoFill in the search bar. Double click the entry, change the entry to True. Source
Well, that's all I've found/needed so far. What else is there? 
Edit for consolidation:
aesman:I read the link and it is the same as what jimmyrcom says in the video.
For - true/30
Don't forget
network.http.max-persistent-connections-per-server I set mine to "50"
GiddyUpGo:Firefox has an option that thinks it knows
which pages you will need and pre-loads them, even tho you might not
even use them. Setting this option from true to false will speed up
your browser plus save you bandwidth those pre-loaded pages take up.
Normal
0
Under About:config search for:
network.prefetch-next
toggle it from true to false
GiddyUpGo:If you are still wanting tips, here is a good site that lists how to use Firefox 3 plus a lot of how-to-do tweaks.
http://www.tweakguides.com/
Add (note these values, especially, will depend on your connection speed)
aesman:Double Click on the following settins and put
in the numbers below - for the true / false booleans - they’ll change
when you double click.
Code:
network.http.max-connections – 48
network.http.max-connections-per-server – 16
network.http.max-persistent-connections-per-proxy – 8
network.http.max-persistent-connections-per-server – 4
network.http.pipelining – true
network.http.pipelining.maxrequests – 100
network.http.proxy.pipelining – true
One
more thing… Right-click somewhere on that screen and add a NEW ->
Integer. Name it “nglayout.initialpaint.delay” and set its value to
“0”. This value is the amount of time the browser waits before it acts
on information it receives. If you’re broadband - it shouldn’t have to
wait.
Now you should notice you’re loading pages MUCH faster now!