Hey! tl;dr? Click here to go directly to the fast improvements post and disable some unwanted services.
Still want more fun disabling services? Read the second post.
I improved the speed of my G2 recently and felt that the community might appreciate this as well. It's probably not the "best guide" for everybody, but this is what I've done and it's worked nicely for me so far.
I recently got irritated at my phone being occasionally sluggish. So, when it was sluggish one time, I went to Manage applications->Running Applications, and saw that Facebook decided it wanted to start itself up in the background.
Now, I'm as big a fan as the next guy for having multi-tasking, but randomly starting an app in the background without my consent is not what I consider to be useful or resource-friendly. I decided to "freeze" the app using SD Maid (you can do this with Titanium Backup as well). Facebook is now in a frozen state so it will not launch itself at all. Ha!
What do I do about having no Facebook now? Well, there happens to be a great app on the Market called Fast for Facebook. This is quite an improvement over the sluggish and buggy Facebook app. I installed that and am having a blast with it so far.
I wanted to check for other apps that were dawdling in the background. So I looked again in Running Applications and found that Maps decided it wants to be running too. I went to the settings for the Maps application, and turned off Location reporting. Why would I want an app sucking my resources dry to alert the world where I am? I'm not that much of a socialite or stalker prey. I also turned off Automatic check-ins.
Previously, I'd gone through a few other apps and turned off automatic sync. Things like DropSync (to sync Dropbox), Tumblr, Google+, and Twitter are not necessary for me to have reviving themselves in the background. I should be the authoritarian ruler of all of the apps over my phone- no freedom here to run around as you please.
I set up a couple apps to run at odd hours of the night. I only need to have photos and documents synced probably once a day, so I set up Tasker to do it automatically while the phone is charging and connected to Wifi at around 4am. I've set up Titanium Backup to do backups something like every Tuesday night, Friday night, and Sunday night, each at like 4am as well; and upload those backups to Box. I want to use my phone fast when I use it during the day, and at night time it can take its time with these lesser-priority tasks while I'm asleep.
Email/Gmail and Messages still have notifications and syncing, as well as the occasional Pulse RSS feed notification. All else seems to be shutting up though, which is good. What I would really like to do is have Market update its apps automatically at like 4am, so it won't spend resources checking for updates in the background. I can't find how to do that though.
One app that really gets under my skin is Amazon Appstore. This guy runs in the background too- I've turned off its notifications but I'm pretty sure it'll still sit there sapping my resources. This one's a toughie because I want to uninstall or freeze it, but I want to still be able to get good free apps from it once a day. There have been some really good apps and some really bad ones, but the good ones are worth it to me.
I might add in more things to disable. It's been faster so far, so I'll see how it goes over a couple days. One last thing I did was install SetCPU. I use that now instead of CyanogenMod 7's built-in CPU stuff. I don't know if it's a placebo or not, but I seemed to notice a boost in performance from it (not instantly, but in general I see less lag).
Hope this helps someone, best of luck with all of your phones.