Today I finally got through to being able to update my phone to iOS 5, but when I went to check on progress, I find "No sim installed" or something like that.

My sim's in, but the phone's not reading the card.... nor any other card I try and put in.

Anyone know how to fix this? I can't afford to get another phone and this sucks... :/

In most cases, this is a hardware error. Either the pins that touch the SIM (or microSIM if you're using a 4) have been bent, or something else has happened that has caused a connection issue.

In a lot of cases, this can be quickly fixed by an experienced iPhone technician -- if the phone is under warranty, bring it to the Apple store / Genius Bar and they will verify and either repair or replace with a refurbished model. If the phone is not under warranty, do some digging to find a local iThing repair shop and have them fix it for you. It will definitely be cheaper than buying a replacement phone.

I'm very curious as to how upgrading to iOS 5 could have caused it, but if you've already attempted to re-restore to iOS 5 and you cannot get the phone to work, I think those will be your only options.

I have the same exact problem with my phone when i updated to ios 5, my phone has no carrier, no wifi, no bluetooth, and it keeps saying my phone is searching... up in the top left corner. my baseband is blank. idk whats to do i can't use my phone anymore someone give me some advice.

1) You don't have the same exact problem. Her phone is saying "No SIM", yours is blanking the WiFi/Bluetooth/Carrier information. These are not the same issues -- please don't threadjack.
2) Do a search around the forum, this is a somewhat common hardware failure and there's a possibility you can fix this by restoring again to a proper iOS with a fresh baseband (depending on what phone you're using and whether or not you rely on an unlock) and re-jailbreaking, but in most cases this is the result of a bad baseband flash, which leaves the cellular hardware in an unusable state. This can be caused by a hardware failure or a failure during the flashing process. If a restore doesn't fix it, you'll likely need to bring the phone in to Apple.