What's the ruling on praying by raising my hands after the 5 daily prayers (after Salaam) - is this Bida'h? There is a Hadith saying that praying after the 5 daily prayers is acceptable. Is this what's meant? Is it only praying after Tashahhud and before Salaam?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Making Du'a after the obligatory prayers is recommended in Sharia; there are many proofs in the Qur'an and Sunnah that emphasize making Du'a in general or making some particular supplications.
The evidence for making general supplications after obligatory prayers is the Hadith that the Prophet (Sallallahu Alaihi wa Sallam) was asked, which supplication is most readily answered? He said: The one in the middle of the later part of the night and at the end of obligatory prayers" [ al-Tirmizi reported from Abu Umamah ].
The evidence for making particular supplications is the Hadith of Mu'adh that the Prophet (Sallallahu Alaihi wa Sallam) said to him: "O Mu'adh, I love you'. Then the Prophet (Sallallahu Alaihi wa Sallam) said: 'I advise you, say at the end of every prayer اَالَّهُمَّ أعِنِّي عَلَى ذِكِرِكَ وَشُكْرِكَ وَحُسْنِِ عِبَادَتِكَ ('O Allah, aid me in Your remembrance, Your thanks, and in perfecting Your worship)" [Related by Abu Dawood and Nasa'e ].
There are many Hadith proving the fact mentioned above.
As long as making Du'a at the end of the obligatory prayers is recommended in Sharia then the manners of making Du'a is also recommended such as raising hands. Raising hands for Du'a is proved in Sharia through the practice of the Prophet (Sallallahu Alaihi wa Sallam) and through his words. The Prophet (Sallallahu Alaihi wa Sallam) said: "Your Lord is munificent and generous, and is ashamed to turn away empty the hands of His servant when he raises them to Him" [ Abu Dawood and al-Tirmizi ].
Muslim scholars have two different opinions concerning the exact time of the supplication that is made at the end of the prayers. According to some scholars the supplication should be made just before finishing the prayer. Other scholars believe that they should be made after ending the prayer. May be it is appropriate that they be made after finishing the prayers as Ibn Hajar wrote in 'Fath al-Bari'. ' We answer those who say that the supplications should be made just before ending the prayer that the Prophet (Sallallahu Alaihi wa Sallam) ordered us to do forms of remembrance of Allah at the end of the prayers and all the Muslim scholars agreed that this means after ending the prayer. Likewise the supplications should be made after finishing the obligatory prayers' .
Finally, making Du'a after the obligatory prayers is recommended and raising hands for making Du'a is also recommended. Therefore, one should not rebuke the one who practises so. Likewise, the one who adopts the other opinion should not be rebuked both practices are acceptable.
Allah knows best.